在钢筋混凝土楼梯构造中，当荷载或梯段跨度较大时，采用( )比较经济。
A．板武楼梯 B．梁式楼梯C．悬挑式楼梯 D．墙承式楼梯
参考答案：B
发生心室纤维性颤动时，血液循环（）。
A、变化不大
B、中止
C、加快
D、减缓
About ___________of the workers in the factory were born in__________.
A．three-fifths, 1970s
B．three- fifths, the 1970s
C．three- fifth, the 1970s
D．three- fifth, 1970
