The chief engineer of the high-speed railway ________ Shanghai to Beijing always devotes most of his time ________ his work.

What did the boy do just now—He ran______ the road to pick up his ball.

My sister is only four years old, but she can________some English.

Since Tom downloaded a virus into his computer, he cannot open the file now.

or the fact that Mr Smith ________ill yesterday, he would have attended the important meeting.