In order to find out how the famous painting was stolen as soon as possible, more experienced policemen have been sent to _____ the case.
Waiter: Here is the steak you ordered. Please _________and enjoy yourself. Customer: Thank you.
Paper money was in _________ use in China when Marco Polo visited the country in _________13th century.
The audience was _____ very young children so there was a lot of noise while the concert was going on.
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.