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

[Q]: Thermoregulation is the process when animals maintain an internal temperature.
[A]: What is the process when animals maintain an internal temperature?

[Q]: Protons and neutrons are made of quarks, which are fundamental particles of matter.
[A]: A fundamental particle of matter, protons and neutrons are made of these?

[Q]: Voltage is continuously changing within a circuit in an analog signal.
[A]:
What is continuously changing within a circuit in an analog signal?