Final Answer: A book of synonyms is called a thesaurus. It is a tool that helps writers find synonyms and antonyms to improve their vocabulary and writing skills. Hence, the correct answer to the student's question is C. a thesaurus. ; Explanation: A book of synonyms is called a thesaurus. A thesaurus is a reference tool that provides lists of synonyms—words that have similar meanings—as well as antonyms, which are words with opposite meanings. Purpose of a Thesaurus : Its primary function is to help writers find the most suitable word to express their thoughts more precisely. This enhances writing by allowing options beyond the most common words. Structure : Thesauruses often list words alphabetically, and under each entry, you will find a range of synonyms and sometimes antonyms. Usage : Writers, students, and anyone looking to improve their vocabulary will benefit from using a thesaurus. For instance, if you look up the word "happy," you might find synonyms like "joyful," "content," and "pleased." Using a thesaurus alongside a dictionary can greatly improve your writing by ensuring you are using words that best fit your intended meaning, as well as helping you learn new vocabulary. ; Examples & Evidence: For example, if you are writing an essay and you want to use a more interesting word than 'big,' you can look it up in a thesaurus and find synonyms like 'huge,' 'enormous,' or 'gigantic.' This helps make your writing more engaging. Many educational resources and writing courses emphasize the importance of using a thesaurus to enhance writing skills and vocabulary, confirming that it is a widely accepted tool among writers and students. Answer from Kai55 on brainly.com

Final Answer: A book of synonyms is called a thesaurus. It is a tool that helps writers find synonyms and antonyms to improve their vocabulary and writing skills. Hence, the correct answer to the student's question is C. a thesaurus. ; Explanation: A book of synonyms is called a thesaurus. A thesaurus is a reference tool that provides lists of synonyms—words that have similar meanings—as well as antonyms, which are words with opposite meanings. Purpose of a Thesaurus : Its primary function is to help writers find the most suitable word to express their thoughts more precisely. This enhances writing by allowing options beyond the most common words. Structure : Thesauruses often list words alphabetically, and under each entry, you will find a range of synonyms and sometimes antonyms. Usage : Writers, students, and anyone looking to improve their vocabulary will benefit from using a thesaurus. For instance, if you look up the word "happy," you might find synonyms like "joyful," "content," and "pleased." Using a thesaurus alongside a dictionary can greatly improve your writing by ensuring you are using words that best fit your intended meaning, as well as helping you learn new vocabulary. ; Examples & Evidence: For example, if you are writing an essay and you want to use a more interesting word than 'big,' you can look it up in a thesaurus and find synonyms like 'huge,' 'enormous,' or 'gigantic.' This helps make your writing more engaging. Many educational resources and writing courses emphasize the importance of using a thesaurus to enhance writing skills and vocabulary, confirming that it is a widely accepted tool among writers and students. Answer from Kai55 on brainly.com