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 kind of diffusion do small hydrophobic molecules squeeze through lipid molecules.

Answer: What kind of diffusion do small hydrophobic molecules squeeze through lipid molecules?

Question: All enzymes have an optimal temperature and ph.

Answer: All enzymes have an optimal temperature and what?

Question: The decay rate is measured in a unit called the half-life.

Answer:
The decay rate is measured in a unit called the what?