我国第一张信用卡是（）。
A.长城卡
B.金穗卡
C.中银卡
D.牡丹卡
参考答案：A
No sooner _____ themselves in their seats in the theatre _______ the curtain went up.
A．they have settled; before
B．had they settled; than
C．have they settled; when
D．they had settled;than
土壤盐基饱和度就是土壤溶液中盐基离子总量占土壤阳离子交换量的百分数.（）
