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

[Q]: Very low density is the concentration of gas molecules in the mesosphere.
[A]: What is the concentration of gas molecules in the mesosphere?

[Q]: Although they differ vastly in hardness, pencil lead and diamonds both contain carbon.
[A]: Although they differ vastly in hardness, pencil lead and diamonds both contain what element?

[Q]: Neutrophils provide an early, rapid, and nonspecific defense against invading pathogens.
[A]:
What provides an early, rapid, and nonspecific defense against invading pathogens?