.When _____ if he had seen her, Mattew just shook his head.
Driving a car is not so difficult as you imagine, if you _______ the rules.
She has to _______ her journey because of her mother’s illness.
Zhang Lin was addicted to computer games during his last year in high school, otherwise he _______ a student of Beijing University.
The science of the library is sometimes broken by a sudden cough or the sound of pages _______.
Every pupil has his own potential so it is not proper to _______ them _______ two kinds.