What is the most likely cause of the mass extinction that occurred about 65.5 million years ago?
a) The Earth's north and south magnetic poles reversed.
b) A giant asteroid struck the Earth causing global consequences.
c) A rapid mountain-building episode blocked animal migration at that time.
d) Forest fires caused a vast reduction in global oxygen.
e) An increase in the luminosity of the Sun boiled away most of the oceans.
Answer: B