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: Simple carbohydrates can be classified in terms of chain length.

Answer: Which carbohydrates can be classified in terms of chain length?


Question: Sexually do invertebrates reproduce.

Answer: How do invertebrates reproduce?


Question: All matter in the universe is composed of one or more unique pure substances called elements.

Answer:
All matter in the universe is composed of one or more unique pure substances called what?