What typically happens early in the process when two disk galaxies collide?

Question

About 10% of all the stars in the galaxy collide and are destroyed.

The bulges of the two galaxies implode, creating two new supermassive black holes.

Very little happens, because the disks pass right through each other and remain undisturbed.

Two long tails of stars get thrown out of the galaxies into space.

WHICH ONE??

Answer 1

I'd hazard a guess at 3, the outer disk is relatively sparse.

Answer 2

Very little happens, because the disks pass right through each other and remain undisturbed.