instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
Gabbro is a dark dense rock that can be found in the oceanic crust.
answer:
Gabbro is a dark dense rock that can be found in what?


question:
Optics explains the behavior of visible light and electromagnetic waves.
answer:
What type of physics explains the behavior of visible light and electromagnetic waves?


question:
A sarcomere is the smallest contractile portion of a muscle.
answer:

What is the smallest contractile portion of a muscle?