21. ______ is a process by which a word of wider meaning acquires a specialized sense. For example，the original meaning of the word“meat” was food and the modern meaning is edible flesh. ( )
A. Conversion B. Elevating
C. Narrowing D. Formation
22. Which of the following is NOT a context clue? ( )
A. Relevant details. B. Sentence structure.
C. Synonymy. D. Antonymy.
23. The sentence “I like Mary better than John’’ is ambiguous due to ______. ( )
A. grammatical context B. polysemy
C. antonymy D. hyponymy
24. In the sentence“Copernicus believed in a heliocentric universe，rather than in the geocentric theory”，the meaning of heliocentric call be inferred from the clue of ______.( )
A. relevant details B. word structure
C. antonymy D. hyponymy
25. “Tooth and nail” is all idiom ______ in nature. ( )
A. verbal B. nominal
C. adjectival D. adverbial
