题目内容：

    Floating on the surface of the seas of the world are billions of tons of small plants and animals called plankton. Most of these plants and animals are too small for the human eye to see. They move about lazily with the currents, providing a basic food for many larger animals. Plankton has been described as the equivalent (相等的东西) of the grasses that grow on dry land, and the comparison is an appropriate one. In potential food value, however, plankton far outweighs that of land grasses. One scientist has estimated that while grasses of the world produce about 49 billion tons of valuable carbohydrates(碳水化合物) each year, the sea’s plankton produces more than twice as much.

Despite its enormous food potential, little effort was made until recently to farm plankton as we farm grasses on land. Now scientists have at last begun to study this possibility, especially as the sea’s resources appear even more important as a means of feeding an expanding world population.

No one yet has seriously suggested that “planktonburgers” may soon become popular around the world. As a possible farmed supplementary food source, however, plankton is gaining considerable interest among scientists.

One type of plankton that seems to have great harvest possibilities is a tiny creature called krill(磷虾). Growing to two or three inches long, krill are a major food source for the giant blue whale, the largest animal ever to live on the Earth. Realizing that this whale may grow 100 feet and weigh about 150 tons, it is not surprising that each one swallows more than one ton of krill daily.

Krill swim about just below the surface in huge schools sometimes wide, mainly in the cold Antarctic. Because of their pink color, they often appear as an entire reddish mass when viewed from a ship or from the air. Krill are very high in food value. If krill can feed such huge creatures as whales, many scientists reason, they must certainly be competitors among possible new food sources for humans.

1.Which of the following correctly describes plankton?

A. It has a higher food value than grasses. B. It is food for most small sea animals.

C. It can grow on dry land as well. D. It grows up in the deep water.

2.Why does the author mention”planktonburgers” in Paragraph 3?

A. To show scientists’ interest in plankton.

B. To describe the appearance of plankton.

C. To question the food potential of plankton.

D. To suggest plankton as a possible food source.

3.According to Paragraph 4, the blue whale___________.

A. feeds mainly on krill. B. can grow up to 150 feet.

C. suffers from lack of food. D. was born two or three inches long.

4.Which of the following is TURE about krill?

A. They mainly live in the Arcitc. B. They are of great value to humans.

C. They are the smallest sea animals. D. They come in many different colors.