That Mercury has a large iron core is evidenced by
a. the large lobate scarps.
b. the large mean density of Mercury.
c. the lava flows near Caloris Basin.
d. all of the above
e. none of the above
Question 2
A ____ generally contains well over 1000 galaxies and is quite dense. They often contain many giant elliptical galaxies.
a. local group
b. poor cluster
c. rich cluster
d. tidal tail
e. quasar