2008年北京市崇文区中考英语一模试卷(4)

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A．a travel guide

C．a Chinese report B．a Chinese newspaper D．a magazine on shopping

（B）

Fish have ears. Really. They’re quite small and have no opening to the outside world carrying sound through the body. For the past seven years, Simon Thorrold, a university professor, has been examining fish ears, small round ear bones called otoliths（耳石）.

As fish grow, so do their otoliths. Each day, their otoliths get a ring of calcium carbonate（碳酸钙）. By looking through a microscope and counting these rings, Thorrold can tell the exact age of a young fish. As a fish gets older, its otoliths no longer get daily rings. Instead, they get yearly rings, which can also be counted, giving information about the fish’s age, just like the growth rings of a tree.

Ring counting is nothing new to fish scientists. But Thorrold has turned to a new field. They’re examining the chemical elements（元素） of each otolith ring.

The daily ring gives us the time, but chemistry tells us about the environment in which the fish swam on any given day. These elements tell us about the chemistry of the water that the fish was in. It also says something about water temperature, which decides how much of these elements will get together within each otolith ring.

Thorrold can tell, for example, if a fish spent time in the open ocean before entering the less salty water of coastal areas. He can basically tell where fish are spending their time at any given stage of history.

The Atlantic croaker is a popular saltwater food fish. Thorrold and his assistant have successfully followed the traveling of young fish from mid-ocean to the coast, a journey of many hundreds of miles. Of course, this is important to managers in the fish industry because they know nearly nothing about the whereabouts（行踪） of the young fish for most food fish in the ocean. Eager to learn about his technology, fish scientists are now lending Thorrold their ears.

49．Why does thewriter compare the fish to trees?

A．Trees get a growth ring each day.

B．Trees also have otoliths.

C．Their growth rings are very small.

D．They both have growth rings.

50．Why is it important to study the chemistry elements of otolith rings?

A．The elements of the otoliths can tell the history of the sea.

B．Chemical elements of the otoliths can tell how fast fish can swim.

C．We can know more about fish and their living environment.

D．Scientists can know exactly how old a fish is.

51．How can you understand “fish scientists are now lending Thorrold their ears”?

A．They want to know where they can find fish ears.

B．They lend their fish to Thorrold for chemical studies.

C．They are very interested in Thorrold’s research findings.