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

[Q]: Protists are thought to be the oldest eukaryotes.
[A]: What is thought to be the oldest eukaryotes?


[Q]: The vascular structure functions as a framework that reinforces the shape of the leaf.
[A]: What functions as a framework that reinforces the shape of the leaf?


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