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

[EX Q]: Deletions remove one or more nucleotides from the dna
[EX A]: Deletions remove one or more what from the dna?

[EX Q]: A crater can usually be found on the top of composite volcanoes.
[EX A]: A crater can usually be found on the top of what kind of volcanoes?

[EX Q]: When magma reaches the surface through cracks in the earth's crust, a volcanic eruption occurs.
[EX A]:
When magma reaches the surface through cracks in the earth's crust, what occurs?