《2025年名校课堂九年级英语下册人教版安徽专版》

热点速递（2024·铜陵市一模）Most of you may think of clams(蛤蜊）as part of a big meal. But these little things can do an important job：testing the cleanliness of water，including the water people drink.
The main water station in Warsaw，Poland，provides water to millions of people. To ensure the water is clean and safe to drink，the station uses a special way with clams. Every day，eight clams help test the water quality. Clams are very sensitive to water pollution，even detecting very small changes. If the water is not clean enough，the clams will close their shells(壳）.
The workers at the water station monitor the clams closely. They have a system that tracks when the clams close their shells. If the system detects that four or more clams have closed their shells at the same time，it sends a warning to the workers. This allows the workers to take action quickly.
To make sure the clams stay sensitive(敏感的）to their environment，the workers replace them with new ones every three months. The water station has found this way to be very useful in protecting the water. It shows how even the smallest creatures can play an important role in protecting the safety and health of our communities.
21. What important job can clams do according to the passage?（不超过 5 个词）
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22. What will the clams do if the water is dirty?（不超过 5 个词）
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23. Why do the workers choose new clams to work for them sometimes?（不超过 10 个词）
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答案： Testing the cleanliness of water.@@Close their shells. /They will close their shells.@@To make sure the clams stay sensitive to the environment.