【C18】
A.While
B.Once
C.Since
D.Though
请帮忙给出正确答案和分析,谢谢!
【C5】A.untilB.onceC.afterD.since
A.unlessB.onceC.whileD.as
A.ifB.onceC.whenD.whereas
【C17】A.WhileB.AlthoughC.SinceD.So
【C12】A.neverB.onceC.frequentlyD.scarcely
【C6】A.everB.onceC.neverD.still