* A thesaurus is a reference book that lists synonyms (words with similar meanings) for other words.
Let's look at why the other options are incorrect:
* A frequently misspelled words: While dictionaries are helpful for spelling, thesauruses are not specifically designed for this purpose.
* C famous persons: A thesaurus would not contain information about famous persons. That would be the domain of a biographical dictionary or encyclopedia.
* D definitions: While thesauruses may include brief definitions, their primary purpose is to provide synonyms.
In short, a thesaurus helps you find different ways to say the same thing.