Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
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Question: If two populations do not mate and produce fertile offspring, separate species result.

Answer: If two populations do not mate and produce fertile offspring, what results?

Question: Invertebrates (and higher animals) can also be placed in one of two groups based on how they develop as embryos.

Answer: Invertebrates (and higher animals) can also be placed in one of two groups based on how they develop as what?

Question: Four children born at one birth are called quadruplets.

Answer:
What are four children born at one birth called?