What has occurred when large numbers of species die out over a short period of time?

a) mastodon loss

b) mass extinction

c) habitat destruction

d) volcanic eruptions

The thing which could be occurred when large numbers of species die out over a short period of time is mass extinction. If plenty of species dissapear due to particular circumstances it means that they become extinct. This usually happens due to some global events or environmental changes that occured too rapidly.