题目选项分析

According to two teams of paleontologists, recent fossil discoveries in Pakistan show that whales, porpoises, and dolphins are more closely related to some of the oldest known even-toed ungulates--a group of hoofed mammals that today includes cows, camels, pigs, and hippos--than to any other mammals.

According to two teams of paleontologists, recent fossil discoveries in Pakistan show whales, porpoises, and dolphins to be more closely related to some of the oldest known even-toed ungulates--a group of hoofed mammals that today include cows, camels, pigs, and hippos--than they are to any other mammals.