Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Q: Most protein antigens require signals from helper t cells (th2) to proceed to make antibody.

A: Most protein antigens require signals from helper t cells (th2) to proceed to make what?
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Q: Surface tension is responsible for the fact that small insects can walk on water.

A: Surface tension is responsible for the fact that small insects can do this on water?
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Q: Childhood is typically easier for learning multiple languages.

A:
Which stage of life is typically easier for learning multiple languages?
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