Concept:Lexical words (content words) carry real meaning, unlike grammatical words which serve structural roles.
Explanation:- Lexical words include nouns, verbs, adjectives, and most adverbs. They have independent meaning.
- "Principal" is a noun, so it is a lexical word.
- "Some" is a determiner, used to quantify nouns.
- "Whether" and "if" are conjunctions, used to connect clauses.
- Therefore, only "principal" qualifies as a lexical word.
Answer:C. principal