Answer:
Using simple mechanics its D thats because A wouldn't make sense at all and C wouldn't be related, D might be.
So we're left with B and D. So B is wrong becuase that wouldn't affect the shape it depends on how it was created and how much interaction with other galaxies have made (gravity w/ mass). So if you understand Stephen Hawking he said that nature is not perfect and can change. The masses can change and can be collided therefore the answer is:
D
