Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
One example is below.
Q: Earth rotates on its axis once times in one day.
A: How many times does Earth rotate on its axis in one day?
Rationale: The given output correctly poses a question based on the scientific fact given.
Q: The epidermis of a leaf contains openings known as stomata, through which the exchange of gases takes place.
A:
Which part of a leaf contains openings known as stomata, through which the exchange of gases takes place?