Option A: Incorrect. Two out-of-band signals mixing to generate in-band spurious isn't reciprocal mixing - reciprocal mixing is LO phase noise mixing with adjacent signals. Out-of-band mixing isn't reciprocal mixing. Option B: Incorrect. In-phase signals cancelling in mixer isn't reciprocal mixing - reciprocal mixing is LO phase noise mixing with adjacent signals. Signal cancellation isn't reciprocal mixing. Option C: Incorrect. Two digital signals combining from alternate time slots isn't reciprocal mixing - reciprocal mixing is LO phase noise mixing with adjacent signals. Digital time slots isn't reciprocal mixing.