GMAT Reading Comprehension (RC) | Re: An extinction event (also known as a mass extinction or biotic crisis)

I have a query over OA of question 3.

There are two types of extinctions which are mentioned in the passage.
1. Background Extinctions
2. MassExtinctons


An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the amount of life on earth. Such an event is identified by a sharp change in the diversity and abundance of macroscopic life

This clearly says that mass extinctions caused sharp change in the diversity.

So how can we eliminate A over
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