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

[EX Q]: Ultrasound, a diagnostic technology, uses high-frequency vibrations transmitted into any tissue in contact with the transducer.
[EX A]: What diagnostic technology uses high-frequency vibrations transmitted into any tissue in contact with the transducer?

[EX Q]: Light retains its original color under water because frequency remains the same when light is refracted.
[EX A]: Light retains its original color under water because what remains the same when light is refracted?

[EX Q]: Because atoms have equal numbers of positive protons and negative electrons, they possess a neutral charge.
[EX A]:
Because atoms have equal numbers of positive protons and negative electrons, what kind of electric charge do they possess?