Last fortnight the rains came to the parched soils of India after the merciless drought had already sapped the vitality and livelihoood of millions of peasants.

Answer: Option D

Decreased : make or become smaller or fewer in size, amount, intensity, or degree.
Demolished : pull or knock down (a building).
Destroyed : end the existence of (something) by damaging or attacking it.
Drained : cause the water or other liquid in (something) to run out, leaving it empty or dry.
Sapped : gradually weaken or destroy (a person's strength or power).

Synonym of Sapped is Drained