Although most biologists believe that many species are becoming extinct each year because of the activities of humans, relatively few species actually appear on compiled lists of extinct species. What is one reason why so few species are listed as extinct?

A) Many species are unknown to science and go extinct before they've been described.
B) There really aren't that many species that have become extinct.
C) Many species aren't listed because they aren't considered important.
D) Only extinctions that are naturally caused are listed.