I can think of many cases students obviously know a lot of English words and expressions but couldn’t write a good essay.
Dorothy was always speaking highly of her role in the play, ____, of course, made the others unhappy.
He made another wonderful discovery, ______ of great importance to science.
He’s got himself into a dangerous situation _____ he is likely to lose control over the plane.
I met the teacher in the street yesterday ________ taught me English three years ago.
Is this all that you need? If you married me, I’d give you everything you _____.