What is the standard way to express radio frequency in aviation?

In aviation, the standard way to express radio frequency is by using separate digits, which allows for clarity and ease of communication among pilots and air traffic controllers. Frequencies are generally presented in a format that consists of a whole number followed by three additional digits. For example, a frequency might be expressed as 125.75 MHz, where the first part represents the megahertz value, and each digit is spoken individually during communications. This method reduces the chances of misunderstanding over the radio, where clarity is essential.

The other options, while they may represent frequencies in some context, do not adhere to the standard practice used in aviation. Specifically, using three letters followed by four digits, expressing frequencies entirely in megahertz, or presenting them as a mixed number can lead to confusion and miscommunication, especially in a field where precision is critical. Therefore, the separation of digits provides a clear and unambiguous method for conveying important frequency information.