TASK DEFINITION: Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
PROBLEM: Matter that mechanical wave energy can only travel through is medium.

SOLUTION: What is the name of matter that mechanical wave energy can only travel through?

PROBLEM: Carried through body happens if cancer cells enter the blood stream.

SOLUTION: What happens if cancer cells enter the blood stream?

PROBLEM: Most protein antigens require signals from helper t cells (th2) to proceed to make antibody.

SOLUTION:
Most protein antigens require signals from helper t cells (th2) to proceed to make what?