A professor and a writer _________present at the meeting.
I don't know whether the books __________ to the homeless children next month are really useful.
There was no more than one iPhone 4S in the store, so I had no choice but __________.
The machine has been made easier for it __________.
No matter how bright a talker you are, there are times when it's better __________ silent.
I remembered __________ the door before I left the office, but forgot to turn off the lights.