Explanation: SINAD stands for **SI**gnal, **N**oise **A**nd **D**istortion. It is a critical metric used to quantify the quality of a signal, often in the context of receiver performance or system fidelity. Option B accurately defines SINAD. It represents the ratio of the total power of the received signal (which includes the desired signal, plus any unwanted noise and distortion) to the power of the unwanted components alone (noise and distortion). Mathematically, SINAD = (Signal + Noise + Distortion) / (Noise + Distortion). A higher SINAD value indicates a cleaner signal and better system performance, as the desired signal power is significantly greater than the combined power of noise and distortion. Options A and D are incorrect because they involve products of components, which do not correspond to the standard definition of SINAD. Option C describes the inverse of SINAD, measuring the unwanted components relative to the total, rather than the total relative to the unwanted.