The Relationship Between a Galaxy and the Galaxy Cluster of Which

Multiple Choice

The relationship between a galaxy and the galaxy cluster of which it is a part is similar to the relationship between a galaxy cluster and the supercluster of which it is a part, with one important difference. What is that difference?

A) Clusters contain only like galaxies (spirals, etc.) ; superclusters combine clusters of various types.
B) Superclusters rely on copious amounts of dark matter to bind them together; clusters do not.
C) A cluster is a gravitationally bound system; a supercluster is not.
D) The galaxy clusters in a supercluster orbit an enormous black hole; this is not the case with the galaxies in a cluster.