Which best expresses the main idea of this passage? A B C D A gigantic climate-changing

Which best expresses the main idea of this passage?
A
B
C
D
A gigantic climate-changing asteroid hitting the earth
is probably what drove the dinosaurs extinct.
Dinosaurs were giant reptile creatures who roamed
the earth millions of years ago.
An unimaginably large volcano eruption probably
caused the dinosaurs to go extinct.
Scientists have varying theories about how and why
the dinosaurs went extinct.