Large groups of galaxy clusters that appear in sheetlike and threadlike shapes are known as a. radio galaxies. b. superclusters. c. large clusters. d. local clusters.

The answer is B. Superclusters

Large groups of galaxy clusters that appear in sheetlike and threadlike shapes are known as superclusters. These are a cluster of galaxies which themselves occur as clusters as well. One example is the Virgo supercluster. It is a mass concentration of galaxies that contains the Virgo Cluster.

they are all solids.