I can think of many cases students obviously knew a lot of English words and expressions but couldn' t write a good essay.
We’ll never forget the days ______ we lived in the country.
He lives in a room _______ faces the south.
Is this dictionary _____ you bought yesterday?
The skirt ______ she spent 50 yuan is very beautiful on her.
He must be from America, ____ can be judged from his accent.