What technique is used to ensure that voice messages containing unusual words are received correctly?

Using a standard phonetic alphabet is an effective technique for ensuring that voice messages containing unusual words are received correctly. Phonetic alphabets, such as the NATO phonetic alphabet, assign distinct words to each letter of the alphabet, which helps to eliminate confusion, especially in a noisy environment or when communicating over radio frequencies.

For instance, instead of saying the letter "B," you would say "Bravo," which is less likely to be misinterpreted than the letter itself. This method is particularly valuable when dealing with names, places, or any special terminology that may be unfamiliar to the listener.

The other choices may not provide the same level of clarity. Speaking loudly could lead to distortion or further misunderstanding if the connection is poor. Sending words in Morse code might not be practical in many situations, especially for immediate voice communications. Thus, utilizing a standard phonetic alphabet stands out as the most reliable method for clear communication of unusual words.