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

[EX Q]: The cardiovascular system in the human body consists of the heart, a network of blood vessels, and blood.
[EX A]: Which system in the human body consists of the heart, a network of blood vessels, and blood?

[EX Q]: The second step in eukaryotic cell division is division of nucleus part of the cell.
[EX A]: The second step in eukaryotic cell division is division of which part of the cell?

[EX Q]: Twice a year often do partial lunar eclipses occur.
[EX A]:
How often do partial lunar eclipses occur?