Answer: Option A
Explanation:
The extinction of the dinosaurs took place approximately 66 million years ago.This was caused due to catastrophic event that occurred at that time.
This was caused due to an asteroid that came inside the earth at a very high speed that lead to the mass destruction or extinction of dinosaurs.
After the extinction of dinosaurs, mammals evolved on the earth and became the dominant life form. Mammals are dominant from that time till date.