A VHF frequency channel pair of TX 157.200 MHz and RX 161.800 MHz would most likely be:

Correct Answer: Option D — Both a) and c) are correct

A frequency pair with different transmit and receive frequencies is defined as duplex operation, commonly used by public correspondence coast stations to allow simultaneous two-way communication. This configuration is standard for maritime VHF systems where a shore station must transmit and receive on separate channels to avoid interference.