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(2024·苏州)请认真阅读下面短文，从方框中选择适当的单词或短语，在横线上填入其正确形式。每个单词或短语仅用一次。
Frogs are an environmental warning system. They have skin which takes in whatever is in the environment. This means that if the environment is 1. ____________，a frog's skin takes in the pollution and the frog dies. For this reason, if there's something wrong in the environment, frogs are the first to die. If there are 2. ____________ frogs, it's a good sign that the environment is healthy.
Frog numbers around the world have been dropping at a faster 3. ____________ in recent years than ever before. Up to 200 kinds of frogs have died out 4. ____________ 1980. This is a disaster. Frogs are needed in the food chain as food for animals like snakes, birds and fish. Frogs are also needed in the food chain to eat insects 5. ____________ grasshoppers.
The world needs frogs.
Frogs are an environmental warning system. They have skin which takes in whatever is in the environment. This means that if the environment is 1. ____________，a frog's skin takes in the pollution and the frog dies. For this reason, if there's something wrong in the environment, frogs are the first to die. If there are 2. ____________ frogs, it's a good sign that the environment is healthy.
Frog numbers around the world have been dropping at a faster 3. ____________ in recent years than ever before. Up to 200 kinds of frogs have died out 4. ____________ 1980. This is a disaster. Frogs are needed in the food chain as food for animals like snakes, birds and fish. Frogs are also needed in the food chain to eat insects 5. ____________ grasshoppers.
The world needs frogs.
答案
1. polluted 2. plenty of 3. speed 4. since 5. such as
