Dinosaurs died off during a mass extinction because .
A. they were hit by a giant asteroid
B. the ocean level rose and they drowned
C. a climate change caused plants to die
D. volcanic eruptions engulfed them in lava flows

The answer is A.

Explanation:

The answer is A. Scientists now studying from approximately 66 million years ago in the prehistoric era say that all of the dinosaurs died when the colossal asteroid impacted all of them. This is what started the cretaceous era.

Here you go! I tried my best with explaining my answer.  

answer; /// i believe that the correct answer is (d); /// alternate walking and running;

b

explanation:

because i can