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

[EX Q]: Most protein antigens require signals from helper t cells (th2) to proceed to make antibody.
[EX A]: Most protein antigens require signals from helper t cells (th2) to proceed to make what?

[EX Q]: The seven unique crystal types are defined by faces parts of themselves (parts that intersect at various angles).
[EX A]: The seven unique crystal types are defined by what parts of themselves (parts that intersect at various angles)?

[EX Q]: A method of sexual reproduction that occurs in plants can be described as seeds are produced from the flower of the plant.
[EX A]:
Which statement describes a method of sexual reproduction that occurs in plants?