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

Muscle groups are controlled by the motor cortex .
Muscle groups are controlled by what mechanism?

Control rods play an important role in the modulation of the nuclear chain reaction.
What play an important role in the modulation of the nuclear chain reaction?

Aphotic zone zone is located below 200 meters from the surface.

Which zone is located below 200 meters from the surface?