We should throw the rubbish into the dustbin ______ protect our environment.
---I think communication by email is better and much easier. Do you think so?---__________, I agree with you.
--He’s never visited the USA before, ________ he?--___________. He plans to go there again next summer.
Don’t get off the bus __________ it stops.
--How long ________ you _________ this book?--For about one week. I ________ it from the library last Tuesday.
---Has he returned from Canada_________?--- Yes, he’s _________ come back.