Explanation: A flip-flop circuit is a fundamental component of sequential digital logic, designed to store a single bit of binary information. A binary digit (bit) can exist in one of two distinct, *stable* electrical states: a logical '0' (typically a low voltage) or a logical '1' (typically a high voltage). Therefore, a single flip-flop has **2** stable states. It can "flip" from one state to the other and "flop" into one, remaining there until triggered to change. This two-state nature is why flip-flops are essential for building memory elements, counters, registers, and frequency dividers found in modern amateur radio equipment like synthesizers, DSPs, and microcontrollers. Options A, B, and D are incorrect because a single flip-flop, by definition, stores one binary digit, which has only two possible values or states.