It is bad manner to ___ other people behind their backs.
A.do up
B.do by
C.do away with
D.do down
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___ otherwise directed by a doctor, this medicine should be taken three times a day.
A.Even if
B.Unless
C.Except that
D.As
Passengers may leave bulky articles under the stairs ___ the conductor's permission.
A.at
B.with
C.on
D.in
His parents never intended ___ together with him though they hoped to see him off.
A.live
B.living
C.to have lived
D.to be living
You don't have to worry ___ we are here.
A.while
B.even if
C.though
D.until