Based on current evidence, a supercluster is most likely to have formed in regions of space where

a. the density of matter was slightly higher than average
b. when the universe was very young the acceleration of the expansion was proceeding faster than elsewhere
c. supermassive black holes were present in the very early universe
d. there was an excess concentration of hydrogen gas when the universe was very young.

a. the density of matter was slightly higher than average

Explanation:

Since galaxies have a great mass, they have a great gravitational attraction. This causes nearby galaxies to attract each other and group together to form clusters. Therefore, the higher the density of matter, the greater the mass of galaxies and is most likely to form clusters. Thus, the more massive the clusters, s most likely that superclusters will form.

moving ball hits still ball. mover stops, hit ball moves. momentum transfer.