Galactic collisions ____.
a. are very rare, since few galaxies are in clusters
b. will cause stars in each galaxy to collide and trigger supernova events
c. often trigger bursts of star formation
d. only happen in poor clusters
e. usually break large galaxy into several small ones
Question 2
Large doses of _______________ light can cause sunburn and skin cancers.
Fill in the blank(s) with correct word