In 1845， a deadly disease struck the farms of Ireland， killing all the Lumper potato plants． In another place or time， the death of single crop species （物种） might not have been so important． But in Ireland， in 1845， people depended almost solely on the potato for food． The death of one species caused a terrible famine（饥荒）． Now， some scientists are worried that such a famine could happen again， but on a much wider scale．

    Over the centuries， farmers have discovered thousands of different species of food crops． Each species has special qualities． Some can be grown in very hot or cold climates． Others are not affected by certain diseases． However， you won't find many of these species in your local supermarket． To feed the seven billion people on Earth， most farmers today are growing only species of plants and farming only species of animals that are easy to produce in large numbers．

    For example， in the Philippines， there were once thousands of varieties of rice： now fewer than 100 are grown there． In China， 90 percent of the wheat varieties grown just a century ago have disappeared． Scientists believe that over the past century， we have allowed more than half of the world's food varieties to disappear．

    One solution to this problem is to collect and store the seeds （种子） as many different plant varieties as we can before they disappear． The idea was first suggested by Russian scientist Nikolay Vavilov． In the 1920s and 1930s， he collected around 400，000 seeds from five continents． More recently， others are continuing the work he began．

    In the U．S． state of Iowa， Diane Ott Whealy wanted to protect historic plant varieties， like the seeds her great ﹣grandfather brought to the U．S． from Germany more than a hundred years ago． She and her husband started a place called Heritage Farm， where people can store and trade seeds．

    More importantly， the people at Heritage Farm don't just store the seeds； they plant them． By doing this， they are reintroducing foods into the marketplace that haven't been grown for years． These food species are not just special in terms of appearance or taste． They also offer farmers food solutions for the future， from the past．

（1）What is this passage mainly about？　　

A． The need to protect different food species．

B． How to increase the number of food species．

C． The fact that many food species are dying out．

D． How to prevent food species from disappearing．

（2）Why are some scientists worried that such a famine could happen again？　　

A． Because people depend on certain species of food crops．

B． Because the same deadly disease may attack crops again．

C． Because the world's population is larger than that in 1845．

D． Because farmers grow the same potatoes as those in the past．

（3）The following sentence would best be placed at the end of　　．Meanwhile， thousands of other species are dying out．

A． Paragraph 1

B． Paragraph 2

C． Paragraph 3

D． Paragraph 4

（4）What can we learn from the passage？　　

A． The disease spread very quickly and killed thousands of people in Ireland．

B． Around 80 percent of the rice varieties in the Philippines have disappeared．

C． People have been storing seeds to save plane varieties for less than 100 years．

D． Heritage Farm is the first place in the U．S． for people to store and trade seeds．