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.
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Question: 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.

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


Question: Question: Calcium ion is an example of what kind of messenger? 
Answer: second. 
Sentence: Calcium ion is an example of a second messenger.

Answer: A calcium ion is a prime example of a second messenger.


Question: Question: If the dna from all 46 chromosomes in a human cell nucleus was laid out end to end, it would measure approximately how long? 
Answer: two meters. 
Sentence: If the dna from all 46 chromosomes in a human cell nucleus was laid out end to end, it would measure approximately two meters long.

Answer:
A human cell nucleus typically has 46 chromosomes which, laid out end to end, would measure out to about two meters.