Answer:
Option B, The ancestors grazed on hard grasses, and modern horses graze on soft forest leaves.
Step-by-step explanation:
Before the rise of Miohippus, the horses used to feed on plant and trees leaves. But with the changing climatic conditions, the forests converted into the grassland and then some where around 28 million years ago, Miohippus arose which were grass eating horses. By this period the teeth became harder and the focus was on incisors and molars . After Miohippus, the horse species came with softer teeths as they started feeding on soft leaves of plant and trees.
Hence, it can be said that The ancestors grazed on hard grasses, and modern horses graze on soft forest leaves.
Option B is correct