Which part of the sine-wave expression cannot be varied in accordance with the low-frequency intelligence to create a modulated signal?

In a sine-wave expression, the amplitude, frequency, and phase can be varied to create a modulated signal in accordance with low-frequency intelligence. However, the carrier wave's frequency itself cannot be varied; it remains constant and serves as the baseline for modulation. This ensures that the carrier maintains its identity while the modulation conveys the desired information.