%of all species that have lived on earth are now extinct.
a. < 1
b. < 10
c. < 50
d. > 99

The Answer is D. >99

Explanation:

Of all species that have existed on Earth, 99.9 percent are now extinct. Many of them perished in five cataclysmic events. According to a recent poll, seven out of ten biologists think we are currently in the throes of a sixth mass extinction. Some say it could wipe out as many as 90 percent of all species living today. Yet other scientists dispute such dire projections.

this is a good question! i'll do some research and come back when i have the answer!