This is from an official GMAT paper test. Can someone please help explain? The answer is C. I don't understand why "body" does not have to be plural in order to agree with "other arachnids."

Unlike other arachnids, which have their nerve cells evenly distributed along their bodies, the scorpion's nerve cells are clustered in its head, like a mammal's.

A) bodies, the scorpion's nerve cells are clustered in its head, like a mammal's
B) bodies, the scorpion's head has a cluster of nerve cells, as a mammal does
C) body, the scorpion has a cluster of nerve cells in its head, as a mammal does
D) body, nerve cells are clustered in the scorpion's head, like a mammal's
E) body, a cluster of nerve cells is in the scorpion's head, like a mammal's