Answer:
Option C, Plains
Step-by-step explanation:
All the mountains, hills and plateaus have undulations in their geography. They have subsiding and arising landforms due to which the geography is not continuous. In such discontinuous platforms the grass land cannot be vast.
However, in planar geographies devoid of any physical barrier, undulations or obstructions, the continuous grasslands on a large chunk of land can appear vast.
Hence, option C is correct