一道语法求教！！！

traviszhu

123. (30997-!-item-!-188;#058&004357)
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.

(A) 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
(B) 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 include cows, camels, pigs, and
hippos--as
(C) 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
(D) whales, porpoises, and dolphins as being 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--as they are
(E) whales, porpoises, and dolphins as 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
A里面的a group of hoofed mammals that today includes中that不是指代mammals吗？那后面怎么用includes啊？

crystalhuang

指a group
A of B that……这种问题的定从指代由句义决定