You are given a question, its answer, and a sentence that supports the question, i.e., the answer to the question is inferable from the sentence. In this task, you need to paraphrase the given sentence so that the paraphrased sentence still supports the question i.e. you can still infer the answer to the question from the paraphrased sentence. Do not write a paraphrase with a minor change in the given sentence e.g. replacing the word "one" with "a". Instead, try to write a paraphrase that contains new words, i.e. the words that are not present in the input sentence.

Q: Question: Reversible reactions are indicated by what kinds of arrows? 
Answer: opposite-headed. 
Sentence: Reversible reactions are indicated by opposite-headed kinds of arrows.

A: If we see the opposite-headed arrows then the reaction is said to be reversible reaction.
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Q: Question: Why is it important to protect soil? 
Answer: It has nutrients used by plants to grow. 
Sentence: It is important to protect soil because it has nutrients used by plants to grow.

A: If soil is not protected, then plants won't have the nutrients they need to grow.
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Q: Question: What process is most responsible for the extinction of most species of plants and animals that have lived on Earth? 
Answer: environmental changes. 
Sentence: Environmental changes is most responsible for the extinction of most species of plants and animals that have lived on earth.

A:
Environmental changes are the main reason why plants and animals, that have lived on the earth, have gone extinct.
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