She needs to improve her ______ of English.

• A. Grammar
• B. Vocabulary
• C. Pronunciation
• D. Fluency

Answer: (B)

This item tests which language area naturally pairs with the phrase “of English” to express what someone needs to grow. The best fit is vocabulary, because vocabulary means the set of words a person knows and can use. When you improve your vocabulary of a language, you’re expanding your word bank, which is a common goal for learners.

The other options are less natural in this construction: grammar refers to rules and structure, and we’d usually say “English grammar” rather than “grammar of English.” Pronunciation is about sounds, typically phrased as “pronunciation in English.” Fluency speaks to the flow of speech and is usually “fluency in English.”