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: Sponges are subdivided into ____ classes.

Answer: three


Question: Some species bear living offspring only every three to ____ years.

Answer: five


Question: Most camera lenses are like a ____ by six picture frame.

Answer:
four