Which one of each sentence that is true about mammals during the Cenozoic era.
a. Many mammals today evolved from primitive mammals with short legs, flat five-toed feet, and small brains.
b. During the Oligocene epoch, a hornless rhinoceros that stood nearly 5 m high had evolved.
c. Saber-toothed cats that evolved during this era can be found in some parts of China today.
d. The mastodon and mammoth died because of major glacial advances.