It was playing computer games _____ cost the boy plenty of time _______ he ought to have spent doing his lessons.
—Why do you look so puzzled? —Oh,I ________ over a most difficult maths problem.
—Peter!Let's hurry.The boss is coming. —Oh,I was afraid that we ________ her.
The past two years ________ a sharp rise in oil price,which adds to the burden of auto transportation industry.
—Jack is always studying hard and does well in all subjects. —No wonder he ________ to be admitted to Beijing University.
Just an hour ago he was telling me on the phone that he ________ home right after the work.