What must occur between transmitter and receiver frequencies?

The correct answer is that the transmitter and receiver frequencies must align. For effective communication between a transmitter and a receiver, they need to be tuned to the same frequency. This alignment ensures that the receiver can adequately pick up the signals transmitted from the transmitter. If the frequencies do not align, the receiver will not be able to interpret the signals properly, resulting in communication failure.

Ensuring frequency alignment is critical in various applications, including radio communications, where specific channels are designated for particular communication purposes. The need for alignment also applies to any system where frequency modulation and demodulation are involved, as the receiver relies on the exact frequency of the received signal to reconstruct the transmitted information accurately.

When considering the other choices, differences in frequency can lead to communication gaps, non-adjustable frequencies can create significant limitations in adaptability, and operational status alone does not guarantee compatibility between the transmitter and receiver without frequency alignment. Thus, alignment is essential for successful communication.