第1题：
Passage Five
The Northern Pike is a very bad fish. It is a big, hungry fish, and swallows little fish such as trout and perch. Many Northern Pikes live in Lake Davis. They are killing all the smaller fish in the lake. The Northern Pike are a serious threat to the lake because they eat all the smaller fish. Soon, all other species of fish in the lake will be killed off. This is not healthy for the environment.
Experts are afraid that the Northern Pike will swim out of Lake Davis through many smaller rivers that feed into the lake. They could spread all over the country and damage many other water environments. If that happens, it would be too late to stop the Northern Pike.
For ten years, officials have been trying to remove the Northern Pike from Lake Davis. They haw. tried using nets, explosives and poisons. However, the Northern Pike population is still doing well in Lake Davis. Many people do not like the idea of using poison to kill the fish. They worry that the poi- sons are bad for humans who use the water. No trace of the poisons has ever been found in local wells, however.
Scientists are going to try the poison again. This time, they will drain the lake before they add the poison to the water. A public hearing will be held to talk about the problem.
52. Why are some people against the use of poisons to kill Northern Pike?
A. Fishermen will be poisoned too.
B. The poisons are expensive.
C. They think that wells will be polluted.
D. The lake will become unsafe.
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第3题：
Passage Three
A group of scientists rowing toward the center of a lake saw something shocking. They turned back as fast as they could. What had they seen.? The lake was boiling!
The group was investigating a crater lake in the mountains of St. Vincent. A crater lake is the mouth of a volcano that has been dormant for some time and has filled with water.
This particular crater was the tip of a volcano called Soufriere, which erupted last in 1902. Since that time, it had not shown any signs of action. But in the fall of 1971, mountain climbers who had hiked near the lake returned to the lowlands with strange stories. They said the water had turned yellow and was giving off a smell like burnt eggs. A seething fog was rising from the lake's surface.
Local scientists rushed to Soufriere to see if this might be the beginning of a new volcanic explosion. They found a huge black mass in the middle of the water. It was a great blob 1,000 feet long and 300 feet wide. Lava had pushed up through the bottom of the lake and formed a new island.
The investigators wanted to make sure that the volcano was safe, and that the lava would not over- flow into the surrounding countryside. But they could never reach the island to study it, because the lava was so hot that the water around it bubbled and boiled.
44. This passage is about ______.
A. mountain climbing
B. a boiling lake
C. a new volcanic island
D. a mysterious blob
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第5题：
第6题：
What will scientists do to make sure the poison works this time?
A. They will try some of it themselves.
B. They will use a special kind of poison.
C. They will drain the lake first.
D. They will only put the poison in the wells.
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第8题：
A crater lake is at the tip of a ______.
A. mountain
B. ridge
C. island
D. volcano
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第10题：