Hi! For your first question, yes, you can do that. For example:
...an event that caused mass extinctions and that persisted for 3,000 years.
The event caused something to happen.
The event persisted for a period of time.
For your second question, what if the correct answer were changed to:
** an event that caused the plant and the animal extinction that mark
No, this is not correct for a meaning reason.
If you separate this out in this way ("the plant and the animal"), then you are referring to two different events. But now the word extinction is singular...so it is only one event. So this is illogical.
You'd have to say:
An event that caused the plant and the animal extinctionS that mark...
Even then, this would not be typical—the typical native-speaker construction would be "the plant and animal extinctions." It's not necessary to repeat "the," and you typically want to avoid doing things that unnecessarily add words to a sentence. But it's very unlikely that the GMAT would make you choose between "the plant and animal extinctions" and "the plant and the animal extinctions." That's just too nitpicky, even for the GMAT.
The construction "the plant and the animal extinctions" is also wrong for a different reason that the GMAT wouldn't test. From a scientific perspective, these extinctions were not limited to one type of organism—it wasn't the case, for example, that the plant extinctions all happened in one timeframe and then, in a separate timeframe, the animal extinctions started while all the plants were fine. The extinctions were interwoven / occurring simultaneously. But this requires factual knowledge and the GMAT doesn't expect you to bring in that kind of factual knowledge—so they wouldn't test this.
