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

[EX Q]: When an atom gains or loses an electron it becames a(n) ion.
[EX A]: When an atom gains or loses an electron it becames an?

[EX Q]: There are three quarks in each proton and neutron.
[EX A]: How many quarks are in each proton and neutron?

[EX Q]: Mechanical waves can only trave through matter.
[EX A]:
Mechanical waves can only trave through what?