If we ________ now to protect our mother river ---Li Jiang River , we ‘ll live to regret it.
A. haven’t acted B. won’t act
C. don’t act D. hadn’t acted
Only after Mary read her article a second time _____the spelling mistakes.
A. did she notice B. she noticed
C. does she notice D. she has noticed
--- Tom , why didn’t you answer my call yesterday afternoon?
--- Sorry , I didn't hear the phone . I ___________ asleep.
A. must be B. must have been
C. could be D. should have been
If you want to change for a red one you'll have to pay ___________ $ 20.
A. another B. other C. more D. each
September 18, 1937 is a day _______ all Chinese will remember forever.
A. when B. what C. 不填 D. why
There are some health problems that , when _______ in time , can become bigger ones later on.
A. not treated B. not having treated
C. not to be treated D. not having been treated
