The correct answer is Modulation. Modulation is the process by which a message signal (such as audio or video) is modified with the help of a locally generated carrier signal to make it suitable for transmission over long distances. This process allows the signal to occupy a desired frequency band and improves its propagation characteristics.
On the other hand, scrambling refers to the intentional alteration of a signal to make it unintelligible to unauthorized users, often used for signal security or subscription services.