Inside of Galaxy Clusters, Which of These Components Contains About

Multiple Choice

Inside of galaxy clusters, which of these components contains about twice as much mass as the stars inside the cluster's galaxies?

A) large numbers of cool, dark, brown dwarf stars floating in the galaxy cluster
B) very hot intergalactic gas emitting X-rays in clusters.
C) a tremendous flux of neutrinos, which have recently been shown to have mass, coming from these clusters.
D) large numbers of small but massive black holes within every galaxy.