III. Cloze        The horse of 50 million years ago, called the Dawn Horse, wasa little animal the size of a fox terrier. The species had four toes oneach front foot and three toes on each hind foot. Its “toenails” werelittle hooves. When this creature lived, there were no grasslands. Itshome was the forest, __19__ it fed on tender shoots and leaves.       There is proof that this little creature was __20__ of the horseof today. Scientists have excavated fossils of certain animals thatlived a few million years later and found that, __21__ they werebigger than the animal of earlier times, they resembled it and themodern-day horse.       The horse family survived when many other animals died out__22__ it had two advantages. The little horse was swift, as wecan guess from its slim body and slender legs. It also was fairlyintelligent； its skull shows that its brain was large __23__ its body.
【題組】19.
(A) that
(B) which
(C) on which
(D) where