Final answer:
Linguists use semantics to study the difference between denotative meanings of words. Semantics is part of linguistics focused on word meanings and their use.
Step-by-step explanation:
Linguists use semantics to investigate the difference between denotative meanings. Denotative meaning is the literal meaning of a word, in contrast to the feelings or ideas that the word suggests. It is a part of the larger field of linguistics that deals with word meanings and word relations, and is concerned with the analysis of the meanings of words, phrases, sentences, and texts.
While phonetics focuses on the sounds of speech, lexicography is the process of compiling dictionaries, and syntax involves the arrangement of words and phrases to create well-formed sentences, it is semantics that specifically addresses how meaning is conveyed through words and symbols. Hence, the correct answer to the student's question would be C) Semantics.