Explanation: A monostable multivibrator, also known as a "one-shot" multivibrator, is a type of sequential logic circuit. It has one stable output state. When an input trigger pulse is applied, the circuit switches to its temporary, unstable (meta-stable) state. It remains in this unstable state for a predetermined period, which is set by its internal resistance and capacitance values, and then automatically returns to its original stable state. This behavior makes it ideal for generating a single output pulse of a specific, controlled duration in response to an input signal, or for creating timed delays. * **Option B** describes an *astable* multivibrator, which continuously oscillates between two unstable states, acting as a clock. * **Option C** describes a *bistable* multivibrator (or flip-flop), which has two stable states and is used for storing one bit of data. * **Option D** describes a *voltage regulator*, a circuit designed to maintain a constant output voltage.