Given the task definition, example input & output, solve the new input case.
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
Example: Earth rotates on its axis once times in one day.
Output: How many times does Earth rotate on its axis in one day?
The given output correctly poses a question based on the scientific fact given.

New input case for you: Knees and elbows are examples of the joints of the skeletal system.
Output:
Knees and elbows are examples of what part of the skeletal system?