What is your teacher doing _____ vacation? [ ]
A. to
B. of
C. with
D. for
答案：D
My name is Lucy. I'm from _____________. [ ]
A. China
B. Canada
C. America
桥梁钢筋混凝土墩台施工中，当墩台高度较大，混凝土下落高度超过( )m时，要使用漏斗、串筒。
A．1B．2C．3D．5
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