A.After all the guests had come
B.By the time all the guests come
C.When all the guests will come
D.Until all the guests come

A.they want to
B.who wanted
C.want to
D.wanting to

A.advantaged
B.disadvantaged
C.advantageous
D.advantageously

A.looked up
B.sent off
C.called up
D.took off

A.didn’t he
B.don't they
C.did they
D.didn't they

A.cold viruses
B.scientists
C.people
D.common colds

A.often caught colds
B.never caught colds
C.suffered a lot
D.became very strong

A.I didn't visit Canada two years ago.
B.I have paid a visit to Canada since last year.
C.I have been in Canada for two years.
D.I haven't come back to Canada for two years.

A.I didn't visit Canada two years ago.
B.I have paid a visit to Canada since last year.
C.I have been in Canada for two years.
D.I haven't come back to Canada for two years.

A.The father asked Tom to play with the knife.
B.The father warned Tom not to play with the knife.
C.The father accused Tom of getting a cut.
D.The father ordered Tom to get a cut.