Hethebookanddecidedthathewould

How does an ecosystem（生态系统）work? What makes the populations of different species the way they are? Why are there so many flies and so few wolves? To find an answer, scientists have built mathematical models of food webs, noting who eats whom and how much each one eats.

With such models, scientists have found out some key principles operating in food webs. Most food webs, for instance, consist of many weak links rather than a few strong ones. When a predator（掠食动物）always eats huge numbers of a single prey（猎物）, the two species are strongly linked; when a predator lives on various species, they are weakly linked. Food webs may be dominated by many weak links because that arrangement is more stable over the long term. If a predator can eat several species, it can survive the extinction（灭绝）of one of them. And if a predator can move on to another species that is easier to find when a prey species becomes rare, the switch allows the original prey to recover. The weak links may thus keep species from driving one another to extinction.

Mathematical models have also revealed that food webs may be unstable, where small changes of top predators can lead to big effects throughout entire ecosystems. In the 1960s, scientists proposed that predators at the top of a food web had a surprising amount of control over the size of populations of other species---including species they did not directly attack.

And unplanned human activities have proved the idea of top-down control by top predators to be true. In the ocean, we fished for top predators such as cod on an industrial scale, while on land, we killed off large predators such as wolves. These actions have greatly affected the ecological balance.

Scientists have built an early-warning system based on mathematical models. Ideally, the system would tell us when to adapt human activities that are pushing an ecosystem toward a breakdown or would even allow us to pull an ecosystem back from the borderline. Prevention is key, scientists says because once ecosystems pass their tipping point（临界点）, it is remarkably difficult for them to return.

（1）What have scientists discovered with the help of mathematical models of food webs？

A．	The living habits of species in food webs.
B．	The rules governing food webs of the ecosystems.
C．	The approaches to studying the species in the ecosystems.
D．	The differences between weak and strong links in food webs.

（2）A strong link is found between two species when a predator______.

A．	has a wide food choice
B．	can easily find new prey
C．	sticks to one prey species
D．	can quickly move to another place

（3）What will happen if the populations of top predators in a food web greatly decline？

A．	The prey species they directly attack will die out.
B．	The species they indirectly attack will turn into top predators.
C．	The living environment of other species will remain unchanged.
D．	The populations of other species will experience unexpected changes.

（4）What conclusion can be drawn from the examples in Paragraph 4？

A．	Uncontrolled human activities greatly upset ecosystems.
B．	Rapid economic development threatens animal habitats.
C．	Species of commercial value dominate other species.
D．	Industrial activities help keep food webs stable.

（5）How does an early-warning system help us maintain the ecological balance？

A．	By getting illegal practices under control.
B．	By stopping us from killing large predators.
C．	By bringing the broken-down ecosystems back to normal.
D．	By signaling the urgent need for taking preventive action.

题型：未知
难度：未知

收藏答案/解析

I must have always known reading was very important because the first memories I have as a child deal with books. There was not one night that I don't remember mom reading me a storybook by my bedside. I was extremely inspired by the elegant way the words sounded.

I always wanted to know what my mom was reading. Hearing mom say," I can't believe what's printed in the newspaper this morning," made me want to grab it out of her hands and read it myself. I wanted to be like my mom and know all of the things she knew. So I carried around a book, and each night, just to be like her, I would pretend to be reading.

This is how everyone learned to read. We would start off with sentences, then paragraphs, and then stories. It seemed an unending journey, but even as a six-year-old girl I realized that knowing how to read could open many doors. When mom said," The C-A-N-D-Y is hidden on the top shelf," I knew where the candy was. My progress in reading raised my curiosity, and I wanted to know everything. I often found myself telling my mom to drive more slowly, so that I could read all of the road signs we passed.

Most of my reading through primary, middle and high school was factual reading. I read for knowledge, and to make A's on my tests. Occasionally, I would read a novel that was assigned, but I didn't enjoy this type of reading. I liked facts, things that are concrete. I thought anything abstract left too much room for argument.

Yet, now that I'm growing and the world I once knew as being so simple is becoming more complex, I find myself needing a way to escape. By opening a novel, I can leave behind my burdens and enter into a wonderful and mysterious world where I am now a new character. In these worlds I can become anyone. I don't have to write down what happened or what technique the author was using when he or she wrote this. I just read to relax.

We're taught to read because it's necessary for much of human understanding. Reading is a vital part of my life. Reading satisfies my desire to keep learning. And I've found that the possibilities that lie within books are limitless.

（1）Why did the author want to grab the newspaper out of mom's hands？

A．	She wanted mom to read the news to her.
B．	She was anxious to know what had happened.
C．	She couldn't wait to tear the newspaper apart.
D．	She couldn't help but stop mom from reading.

（2）According to Paragraph 3, the author's reading of road signs indicates___________.

A．	her unique way to locate herself
B．	her eagerness to develop her reading ability
C．	her effort to remind mom to obey traffic rules
D．	her growing desire to know the world around her.

（3）What was the author's view on factual reading?

A．	It would help her update test-taking skills.
B．	It would allow much room for free thinking.
C．	It would provide true and objective information.
D．	It would help shape a realistic and serious attitude to life.

（4）The author takes novel reading as a way to___________.

A．	explore a fantasy land
B．	develop a passion for leaning
C．	learn about the adult community
D．	get away from a confusing world

（5）What could be the best title for the passage？

A．	The Magic of Reading
B．	The Pleasure of Reading
C．	Growing Up with Reading
D．	Reading Makes a Full Man

题型：未知
难度：未知

收藏答案/解析

History Fair Competition

Understanding history is vital to understanding ourselves as a people and as a nation.

History is much more than the study of dusty old objects and events long past. It is an essential part of who we are today and who we will become. Thornton fiddle School History Fair Competition makes understanding history exciting, engaging, and fun！

This Year's Theme

All participants must address how communication or transportation technology has promoted the quality of life for Americans throughout history. To many people, technology means computers, hand-held devices, or vehicles that travel to distant planets. However, technology is also the application of scientific knowledge to solve a problem, touching lives in countless ways.

Individuals or groups may enter one of the following categories:

Performance

Documentary（纪实作品）

Essay Writing

Category Requirements

Performance: A dramatic presentation of the topic no more than 10 minutes long. If special clothes are used, they should truly represent a given period.

Documentary: A visual presentation（such as a video, slide show, or computer project）no more than 10 minutes long. A desktop computer, screen, projector, and loudspeakers will be available. Students must provide their presentations on CDs before Friday, March 23.

Essay Writing: An academic paper of 2, 000 to 2, 500 words. No illustrations（图解）are allowed. Please do not include covers. A list of references must be included.

Important Dates

January 5

Submit a topic proposal to your history teacher. The teacher may require a second proposal if the first is off-topic or unclear.

February 5

Submit a first draft of your essay, performance script（剧本）, or documentary highlights.

February 19

A committee of teachers will evaluate materials and give opinions. Students then have an opportunity to improve their products.

March 9

Submit a final draft of your essay.

March 15

Performance and documentary committee preview

March 24

Thornton Middle School History Fair Competition

7:00A.M-9:00A.M Participants signing in at the gym

10:00A.M. -6:00PM. Competition and judges' review

7:00P.M. Awards ceremony and picnic

（1）According to Paragraph 1，what is the major goal of understanding history？

A．	To preserve national traditions.
B．	To prepare for a history competition.
C．	To better know the present and future.
D．	To further explore historical mysteries.

（2）What is the theme of this year's competition?

A．	Technology advances science.
B．	Science interacts with technology.
C．	Science has made the study of history easy.
D．	Technology has improved the life of Americans.

（3）Among the items provided by the school for a visual presentation are__________.

A．	special clothes and a screen
B．	a desktop computer and a CD
C．	a projector and special clothes
D．	a desktop computer and loudspeakers

（4）What would a participant have to do with an essay of 1,500 words to meet the category requirement?

A．	Include more information in the essay.
B．	Remove the references.
C．	Provide a cover for the essay.
D．	Explain the details with illustrations.

（5）What will the committee of teachers do on February 19?

A．	Preview performances and documentaries.
B．	Make comments on the materials.
C．	Improve the participant's first draft.
D．	Collect a second proposal from the participant.

题型：未知
难度：未知

收藏答案/解析

阅读下面短文，掌握其大意，然后从各题所给的A、B、C、D四个选项中，选出最佳选项。

I was ready to pay for my bananas at the grocery one night, when fear seized me. My wallet was gone. I could only have left it on the G9 bus, which was now speeding in the dark to some 1 station.

The 2 moment was quickly followed by mental math. How much time and money would it cost to replace the 3 of that little wallet？The credit cards, the driver's license, the cash, all lost to the bus.

Two hours later, back at my house, I heard a knock on the door. My husband 4 it while I was on the phone in the dining room. "Does Jennifer live here?" I heard a lady say. In my husband's hand was my wallet, with not a penny 5 . She left before I could 6 make it to the door to offer my thanks.

After sharing the story online, I heard from someone, who 7 the lady as Erin Smith. Without 8 , I called to thank her. She said she 9 my wallet on a bus seat. She 10 that going to a stranger's house was a 11 move, but she decided to take the chance. "If I were in that 12 . I would want someone to try to find me," she said.

This one stranger responded beautifully to my small 13 , but she actually wasn't the only one. Right after Erin 14 my wallet on the bus, she posted a picture of my driver's license to an online forum（论坛）, trying to see 15 anyone knew me. No sooner did she leave my doorstep than I had emails from two women whose kids go to my son's nursery and who recognized my face. I've never 16 words with those moms beyond small talk, but they wanted to help. I read that people are more divided than ever, but that's not how the people I 17 tend to act.

18 , I feel blessed someone had wanted to help a stranger. Erin had gone 19 what almost anyone would have done, finding my house on a bitterly cold night, and for that I was extremely 20 .

1.

A．

accessible

B．

hidden

C．

unknown

D．

convenient

2.

A．

face-saving

B．

brain-washing

C．

eye-catching

D．

heart-stopping

3.

A．

parts

B．

contents

C．

details

D．

ingredients

4.

A．

ignored

B．

answered

C．

examined

D．

interrupted

5.

A．

missing

B．

returned

C．

remaining

D．

abandoned

6.

A．

still

B．

ever

C．

yet

D．

even

7.

A．

selected

B．

appointed

C．

identified

D．

defined

8.

A．

delay

B．

alarm

C．

regret

D．

invitation

9.

A．

moved

B．

placed

C．

opened

D．

spotted

10.

A．

disagreed

B．

complained

C．

calculated

D．

recommended

11.

A．

selfless

B．

risky

C．

slow

D．

personal

12.

A．

site

B．

direction

C．

situation

D．

atmosphere

13.

A．

crisis

B．

danger

C．

threat

D．

failure

14.

A．

got rid of

B．

made use of

C．

had control of

D．

took possession of

15.

A．

if

B．

where

C．

how

D．

when

16.

A．

recalled

B．

exchanged

C．

repeated

D．

whispered

17.

A．

encounter

B．

follow

C．

consult

D．

accompany

18.

A．

Going away

B．

Turning around

C．

Looking back

D．

Coming along

19.

A．

into

B．

against

C．

over

D．

beyond

20.

A．

longing

B．

enthusiastic

C．

concerned

D．

grateful

题型：未知
难度：未知

收藏答案/解析

A dog's eating habit requires regular training before it is ___________ established.

A．

properly

B．

widely

C．

originally

D．

temporarily

题型：未知
难度：未知

收藏答案/解析