This question is about identifying synonyms and antonyms. The correct answer is D because 'drought' is the opposite of a 'deluge', indicating a lack of water. Options A, B, and C are all synonyms for 'deluge', referring to an excessive amount of water. 'Flood' and 'inundation' both describe situations where an area is covered by water, and 'overflow' refers to the action of water spilling over the edge of a container or area.