Which of these statements expresses a key assumption in our most successful models for galaxy formation?

(A) The distribution of matter was perfectly uniform early in time.

(B) Some regions of the universe were slightly denser than others.

(C) Galaxies formed around supermassive black holes.

(B) Some regions of the universe were slightly denser than others.

Explanation:

According to the Big Bang theory, after recombination, that is, when electrons and protons first became bound to form hydrogen atoms, some slightly denser regions of the almost uniformly universe, grew gravitationally, becoming denser, forming clouds, stars and galaxies.