The twin sisters have learned a lot ________ they came to China.
I have ____________ homework to do and I’m _______ tired now.
The problem is _________ difficult ________ students can solve them.
---Why don’t you go out to play, Rose?---I’m afraid I can’t. I have much homework _______.
---Jim, is there __________ in today’s newspaper? ---No,nothing.
When I______ at the hotel,it was very late.