If he had spent more time practicing speaking English before, he _____ able to speak it much better now.

—Artistic people_________be very difficult sometimes． —Well，you should know you married one．

—May I smoke here ?—If you ____, choose a seat in the smoking section. 

I told your friend how to get to the hotel， but I perhaps I __________ have driven her there.  

If I ______ about this computer program, a hage amount of time and energy would have been saved.