Which word means to add to something, especially in order to make up for a deficiency?

• A. Supplement
• B. Supplementary
• C. Sustain
• D. Tacit

Answer: (A)

The idea being tested is finding a word that means to add something in order to complete or compensate for a deficiency. The best choice is supplement, used as a verb to mean adding to something to improve it or make up for a shortfall. For example, you can supplement your diet with vitamins, or supplement income to cover costs. It emphasizes the act of adding to fill a gap.

Supplementary is an adjective describing something that serves as a supplement, not the act of adding. Sustain means to maintain or support over time, which isn’t about filling a deficiency. Tacit means understood or implied without being stated, which is unrelated to adding or compensating.