To Map Out How Clusters of Galaxies Are Distributed in the Universe

Multiple Choice

To map out how clusters of galaxies are distributed in the universe, astronomers needed to know where each cluster was in the sky AND

A) how many galaxies were in each cluster
B) how blue or red the galaxies in each cluster were
C) how far away from us each cluster was
D) whether any of the galaxies in each cluster acted like quasars
E) whether any gravitational lensing could be seen in each cluster