A.So long as you pay all the bills at once, you can stay in the flat longer.
B.Whether you pay all the bills at once or stay in the flat longer.
C.Without all the bills paid, you can stay in the flat longer.
D.Unless the flat is free of bills, you cannot stay in it.

A.Such a difficult test is it that they couldn’t do it well.
B.The test is so difficult that they couldn’t do it well.
C.So difficult was the test that they couldn’t do it well.
D.It was such the difficult test that they couldn’t do it well.

A.with
B.were
C.when
D.started

A.with
B.were
C.when
D.started

A.was
B.play
C.making
D.pictures

A.treatment
B.addictive
C.includes
D.relaxation

A.therefore
B.but
C.moreover
D.besides

A.behave
B.allow C. remind D. enter
C.
D.

A.determine
B.pollution C. essential D. charity
C.
D.

A.accurately and objectively
B.harder and harder
C.on social and political purposes
D.with other social scientists