We should expect galaxies to collide fairly often because
a. they are large with respect to their separation distances.
b. galaxies contain large amounts of neutral hydrogen.
c. galaxies occur in clusters.
d. they are large with respect to their separation distances and galaxies occur in clusters.
e. None of the other choices are correct.
Question 2
How long a star can stay on the main sequence depends upon its size.
a. True
b. False
Indicate whether the statement is true or false