(A) Synchronic - concerned with something, especially a language, as it exists at one point in time
(B) Torrential - (of rain) falling rapidly and in copious quantities.
(C) Restraint - a measure or condition that keeps someone or something under control or within limits.
(D) Gluttony - habitual greed or excess in eating
The given word Abstinence means the fact or practice of stopping oneself, holding oneself back from indulging in something, typically alcohol. Option (C) is synonymous to the given word. The options are words with completely different meanings. Hence the answer is option (C).