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

[Q]: Clear mucus is secreted before ejaculation to neutralize acidic urine remaining in the urethra.
[A]: What is secreted before ejaculation to neutralize acidic urine remaining in the urethra?


[Q]: Cancer occurs most often in adults over fifty age.
[A]: Cancer occurs most often in adults over what age?


[Q]: Electrons exist only where the wave is stable.
[A]:
Electrons exist only where the wave is what?