The population of the world is increasing rapidly. By 2020, there could be 7.5 billion people on the earth. Will there be enough food for all these people? Some scientists think fish farming might solve this problem. However, other scientists worry that fish farming could bring serious environmental problems.
Fish farming is not a new thing. There were fish farms in China 3,000 years ago. Today, about one third of the fish we eat comes from fish farms.
Most fish farms raise plant-eating fish. Popular kinds of plant-eating fish are carp, tilapia, and catfish. However, many fish farms are starting to raise meat-eating fish. A popular type of meat-eating fish is salmon. However, it takes up to 5 tons of wild fish to produce just 1 ton of farm-raised salmon. So if this continued, many types of wild fish could become extinct.
Critics (评论家) of fish farming also say that farm-raised fish is unhealthy. They say there are dangerous chemicals (化学物质) in the fish. They also say fish farming pollutes the water. Some people say that the ways of farming being used now won’t produce enough fish anyway. Instead of building fish farms in lakes or near the coast, they say that the fish farms could be moved far out into the ocean. In the future, fish farms might be large cages that move to the ocean.
Which of the following about fish farming is true?

A．It is very popular around the world.

B．It is a new thing in 2010.

C．It appeared in China about thirty centuries ago.

D．It can solve the problem of the world’s population.

_________ is not a kind of plant-eating fish.

A．Carp	B．Catfish
C．Tilapia	D．Salmon

What does the underlined word “extinct” mean?

A．绝种的	B．无家可归的
C．弱小的	D．惊慌失措的

How many reasons do the critics hold against the fish farming?

A．2.

B．3.

C．4.

D．5.

What’s the passage mainly about?

A．One way to control the growth of population.

B．One way to feed more people.

C．One way to catch more fish.

D．One way to save the wild fish.