Given a sentence, fill out the missing word with a 'no' or a number (between zero and ten). You should write the numbers with english alphabet, like: four instead of 4.
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Question: Nitric oxide serves ____ main functions in the body.

Answer: three


Question: Prions are protein molecules which have ____ metastable states.

Answer: two


Question: Ozone is a relatively simple molecule, consisting of ____ oxygen atoms bound together.

Answer:
three