—What about the student in your class, Mr. Wang?—The doctor said that sleep caused him poor memory and poor concentration.
The teachers are doing what they _____ their stuaits.
They were _____ inventors than pure scientists.
Old as the car is, _____ it works quite well.
The stubborn boy didn't _____ so that he missed the chance.
You'd better make a mark _____ you have any questions.