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

Q: An object attached to a spring sliding on a frictionless surface is an uncomplicated type of simple harmonic oscillator.

A: An object attached to a spring sliding on a frictionless surface is an uncomplicated type of what device?
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Q: Hemodialysis has a patient’s blood pass through a length of tubing that travels through an artificial kidney machine.

A: Which form of dialysis has a patient’s blood pass through a length of tubing that travels through an artificial kidney machine?
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Q: Carbon has four valence electrons .

A:
How many valence electrons does carbon have?
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