Which sentence does not contain any errors in comma usage?   A. Kangaroos travel in groups hop on two hind legs, and eat various grasses.   B. Kangaroos travel in groups, hop on two hind legs, and, eat various grasses.   C. Kangaroos travel in groups, hop on two hind legs, and eat various grasses.   D. Kangaroos travel in groups hop on two hind legs and eat various grasses.