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【单选题】某建筑柱下等腰三桩承台，柱子截面尺寸为400mm×600mm，桩布置及承台尺寸如图所示，柱位于承台的形心位置。承台顶面处相应于作用的基本组合值为：轴压力F=1500kN，弯矩M=300kN·m。按《建筑地基基础设计规范》作答。 由承台形心到承台底边距离范围内板带的弯矩设计值M2（kN·m）最接近下列（）项。
A.
490
B.
450
C.
390
D.
350
【单选题】起钻时，发生溢流。首先应采取的措施是什么?()(类别：钻井B)
A.
尽可能快地下钻到井底
B.
下钻到套鞋处
C.
关闭环空并且上提方钻杆
D.
接上钻具内安全阀并关井
【单选题】The Grand Canyon Standing on the rim of the Grand Canyon(大峡谷), gazing across this giant wound in the Earth’’s surface, a visitor might assume that the canyon had been caused by some ancient convulsion...
A.
it was caused by some ancient convulsion
B.
its presence is an embarrassment to the state of Colorado
C.
it looks like an injury on the Earth’s surface
D.
it has caused many visitors to injure themselves