What is a mass extinction? how many have occurred in the last 600 million years?

Starting about 360 million years ago, a drawn-out event eliminated about 70 percent of all marine species from Earth over a span of perhaps 20 million years. Pulses, each lasting 100,000 to 300,000 years, are noted within the larger late Devonian extinction

tissue

explanation:

it is actually formed by geoup of cells which is tissue

b exhibiting favoritism toward the kikuyu people.