In this task, you are given a question and an answer, you would be asked to create the sentence based on the Question-Answer provided. It should be contained within the Question-Answer provided.

Q: Question: What are the most numerous and diverse biochemical compounds? Answer: proteins

A: Proteins are the most numerous and diverse biochemical compounds.
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Q: Question: Boron only occurs naturally in compounds with what element? Answer: oxygen

A: Boron only occurs naturally in compounds with oxygen element.
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Q: Question: Varicose veins are veins that become enlarged because the valves no longer do this? Answer: close properly

A:
Varicose veins are veins that become enlarged because the valves no longer close properly.
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