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【单选题】
My brother while he his bike and hurt himself.A.
had fallen;was riding
B.
fell; were riding
C.
had fallen; rode
D.
fell ; was riding
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举一反三
【单选题】He's trained hard for the last two years. It is ______ he did so well at the track and field meet yesterday. [ ]
A.
no problem
B.
no wonder
C.
no doubt
D.
no way
【单选题】假设S7-200 PLC堆栈的初始状态如下图所示，那么执行OLD指令后，栈顶值为______。
A.
iv0+iv1
B.
iv0·iv1
C.
iv1·iv2
D.
iv1+iv2