Push or Repelling Blast 10' mov, pass through enemies or blocked?

Hi, Push mastery or Repelling Blast move a target 10' right away, without needing for an empty space.

I'm wondering what happens in the following scenario:

Enemy A is in front of me, and behind him there is Enemy B, and behind Enemy B there is an empty square.

I push Enemy A back 10'. What happens?

option A: Enemy A is pushed back 10' through Enemy B. Enemy A ends up on the empty square, without affecting Enemy B.

Option B: Enemy A ends up on Enemy B square, they both fall prone at the end of the turn (without a save).

Option C: Enemy A cannot be pushed on Enemy B square because it's not empty (i don't think this applies, i don't seem to see any reference in the rules supporting this option)

from RAW i thought Option A should be the correct one, my gm is more for option B (and giving them a save)

What's your opinion?