The earth's worst mass extinction was:
a. late devonian
b. ordovician-silurian
c. permian-triassic
d. end triassic
e. cretaceous-tertiary

C. Permian-Triassic

Explanation:

There have been several mass extinctions throughout Earth's history, more specifically five, at least from what is known so far. All of them share one characteristic, more than half of the species on the planet have died out in a very short period of time. Some extinction were more mild, while some very extreme. The most extreme one was the Permian-Triassic extinction with estimated 90-96% of the species going extinct. This extinction put end to the domination of the sinapsids, but from the smaller animals that survived through it, the dinosaurs and the mammals arose.