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

[Q]: Superior sagittal sinus is the largest of the sinuses.
[A]: What is the largest of the sinuses?


[Q]: Some compounds form rigid frameworks called crystals.
[A]: Some compounds form rigid frameworks called what?


[Q]: Nitrate levels and turbidity factors can have the greatest effect on the health of a river system.
[A]:
Which factors can have the greatest effect on the health of a river system?