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

[Q]: The human body has as many as two trillion lymphocytes, and lymphocytes make up about 25% of all of leukocytes.
[A]: The human body has as many as two trillion lymphocytes, and lymphocytes make up about 25% of all of what?

[Q]: Producers in an ecosystem generally get their energy from the sun.
[A]: Where do producers in an ecosystem generally get their energy from?

[Q]: The thickness of magma determines whether a volcanic eruption will be explosive or not.
[A]:
What determines whether a volcanic eruption will be explosive or not?