Final answer:
FBI and NATO are pronounced letter-by-letter, while NASA and TV are pronounced as words.
Step-by-step explanation:
The acronyms that are pronounced letter-by-letter, also known as initialisms, based on the options provided are FBI (Federal Bureau of Investigation) and NATO (North Atlantic Treaty Organization). In contrast, NASA (National Aeronautics and Space Administration) is usually pronounced as a word itself, rather than by its individual letters. The acronym TV, standing for television, is not typically spelled out and is also pronounced as a word.