Question

Which of the following is true regarding extinction?

Answer 1

I would say that B) single events or several causes working together to produce extinction in a short period is referred to as mass extinction, but I am not 100% sure. 

Answer 2

I think it would be D. because in our text book it says and i quote

"The rate of speciation and extinction varies from clade to clade. Some clades contain many species that have survived for long periods of time. Other clades have only a few species, which soon become extinct."