-___ __ have you worked?    -Since 2 pm.

词义替换。—Would you mind passing me the book?—Of course not. I’ll do it right away. 

--________do you go to the dentist? --Let me see, twice a year, maybe.

I think we should give him another chance _______ he has made some mistakes.

 I thought _______ very useful to know the customs of foreign countries.