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

Ex Input:
Superior sagittal sinus is the largest of the sinuses.

Ex Output:
What is the largest of the sinuses?


Ex Input:
Sodium-potassium pumps help nerve cells establish a voltage across their plasma membranes.

Ex Output:
Sodium-potassium pumps help nerve cells establish a voltage across their what?


Ex Input:
Mesosphere atmospheric layer lies above the highest altitude an airplane can go and below the lowest altitude a spacecraft can orbit.

Ex Output:
What atmospheric layer lies above the highest altitude an airplane can go and below the lowest altitude a spacecraft can orbit?