Which of the following statements best summarizes current evidence concerning dark matter in individual galaxies and in clusters of galaxies?
A. Dark matter is the dominant form of mass in both clusters and in individual galaxies.
B. Dark matter is present between galaxies in clusters, but not within individual galaxies.
C. Dark matter is present in individual galaxies, but there is no evidence that it can exist between the galaxies in a cluster.
D. Within individual galaxies, dark matter is always concentrated near the galactic center, and within clusters it is always concentrated near the cluster center.
Answer:A
Which of the following statements best summarizes current evidence concerning dark matter in individual galaxies and in clusters of galaxies?
A. Dark matter is the dominant form of mass in both clusters and in individual galaxies. B. Dark matter is present between galaxies in clusters, but not within individual galaxies. C. Dark matter is present in individual galaxies, but there is no evidence that it can exist between the galaxies in a cluster. D. Within individual galaxies, dark matter is always concentrated near the galactic center, and within clusters it is always concentrated near the cluster center.