—Why did Mr. Green take his 7th grade students to the river yesterday afternoon?—________ the river.
The chairman thought _____ necessary to invite Professor Smith to speak at the meeting.
She ______his number in the phone book to make sure that she had got it right.
You said boys were cleverer than girls. That is _______ I disagree.
With the rapid growth of population, the city______ in all directions in the past five years.
The bell______ the end o f the period rang and we had to stop our discussion.