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

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

A decline in blood flow to kidneys organs stimulates release of the enzyme renin, in turn stimulating the reabsorption of sodium and water.
A decline in blood flow to what organs stimulates release of the enzyme renin, in turn stimulating the reabsorption of sodium and water?

The tidal forces near black holes are so great they can actually tear matter from a companion star.
The tidal forces near what celestial phenomena are so great they can actually tear matter from a companion star?