Consider a pair of identical (typical) screws and held in opposite hands: the right pointed to your left, the left pointed to your right.

Then place them adjacent to each other (the one in your right hand "on top"), and "interleave" their helical threads together.

If I move the bolts around each other as one would twiddle ones thumbs (the top one comes toward you and the bottom one away from you), holding each screw firmly by the head so that it does not rotate, do the heads:

a) move inward
b) move outward
c) remain the same distance from each other?

You should determine the answer without resorting to the actual test