Think about what you had for lunch: Was it a hamburger? A chicken sandwich? Barbecue? What about vegetables? Would it surprise you to learn that what you eat can affect the whole planet?
It can—in a big way. New studies show how food and its production affect the globe and its warming climate. You’ve probably heard of global warming : The temperature is on the rise because humankind has been releasing (排放) amounts of gases into the atmosphere. One of these greenhouse gases is carbon dioxide（二氧化碳）.
What does this have to do with food ? A big part of the carbon dioxide that we put in the atmosphere every year comes from the process of making and eating food. The production of meat contributes a lot of that carbon diode. And much of meat’s contribution comes from beef , which is responsible for releasing even more warming gases into the atmosphere.
The process of making a hamburger ,for example, requires a lot of energy. A cow has to be fed and raised on farmland, and cow waste is a major source of methane (沼气) — an especially powerful greenhouse gas. The cow has to be killed. The meat has to be processed (加工) and shipped to a shop, which takes fuel . Most of the cow won’t even be used for meat that people eat. By the time a hamburger finally lands on a dinner plate, it has made a heavy effect on the environment.
We can reduce the production of global-warming gases by eating less beef .Other kinds of meat like pork and chicken do less harm to the environment—at least in terms of the amount of greenhouse gases released. 
All kinds of meat are harder on the planet than vegetables. To grow and eat a pound of potatoes, for example, sends less than one-quarter pound of carbon dioxide into the air. So changing our diet to less meat and more vegetables, as it turns out, may do the world some good.
The questions asked in the first paragraph are used to _____.

A．show the author’s concern about food safety

B．express the author’s puzzlement at what to eat

C．remind readers of something delicious to eat

D．introduce the topic to be discussed in the passage

What is the bad news for meat-eaters?

A．Meat producing can cause global warming

B．Most cows are raised not for people to eat

C．There is a lot of carbon dioxide in meat

D．Animals begin to die off because of global warming

Which is the most environment-friendly food according to the passage?

A．Beef

B．Carrot

C．Pork

D．Chicken

The author wrote the passage in order to _____.

A．explain the importance of eating meat	B．advise people to keep a balanced diet
C．encourage people to choose a greener diet	D．introduce some healthy foods to people