The correct answer is (D) Member of a small ruling group; member of an oligarchy; one of the rulers in an oligarchy (i.e. of a state governed by the few).

Oligarch comes from Greek oligarkhes (oligoi [few] + arkho [rule]).

Examples of use:

• Che preferred the excitement of fomenting revolution to life as an oligarch.
• In contrast, the leading soviet communists preferred lives as oligarches.