General exam question G7B07

WhyThe basic components of a sine wave oscillator are a filter and an amplifier operating in a feedback loop. A sine wave oscillator needs a frequency-selective filter (or resonant element) to set the operating frequency and an amplifier to make up for the filter's losses, connected in a feedback loop so the circuit sustains its own oscillation, answer D. An amplifier-and-divider or multiplier-and-mixer combination doesn't provide the frequency-selective feedback a sine oscillator needs, and a feed-forward loop, by definition, doesn't feed the signal back to sustain oscillation, so A, B, and C are wrong.