Work hard at your lessons, ______ you’ll fail the exams again.
The number of the people in the room_______sixty, but a number of them_________students.
What did he say? I don’t know what________.
I told your friend how to get to the hotel, but perhaps I______have driven her here.
I’m sorry to have hurt you, but I didn’t do it________.
It is the first time that I_______to Beijing.