Which of the following is true regarding extinction?

AExtinction that occurs in a relatively short period of time is referred to as background extinction.

BSingle events or several causes working together to produce extinction in a short period is referred to as mass extinction.

CIf the rate of speciation in a clade is equal to or less than the rate of extinction, the clade will survive.

DThe rate of extinction is steady from clade to clade as are the number of species contained within a clade.