阅读下列四篇短文，从每小题后所给的A,B,C或D四个选项中，选出最佳选项。
A recent study of ancient and modern elephants has come up with the unexpected conclusion that the African elephant is divided into two distinct (不同的) species.
The discovery was made by researchers at York and Harvard Universities when they were examining the genetic relationship between the ancient woolly mammoth and mastodon to modern elephants—the Asian elephant, African forest elephant, and African savanna elephant.
