Air masses are formed when the air above huge homogeneous areas acquires the characteristics of the area. This leads to the air having little horizontal variations in form. Accordingly,

C is correct, as it is a cold, large and homogeneous mass of land.

A is incorrect, as the size of the forested areas are not large enough to create air-mass

B is incorrect, as Himalayas do not constitute a homogeneous platform.

D is incorrect due to regional variations across the Deccan Plateau.