The correct answer is - Permian.
The extinction that appeared at the end of the Permian period, also, very often referred to as the ''Great Dying'', occurred about 252 million years ago. It is the boundary of the Permian and Triassic periods. This extinction had taken place because of multiple factors, including the devastating eruptions of multiple super-volcanoes, especially the Siberian one, as well as lots of earthquakes, and sudden climate change.
Because this all happened in such a short period of time, very big portion of the living organism didn't had time to adept, so they died out. The percentage of species that have died out during this extinction event are estimated to be between 90% and 96%.