公路桥梁中的荷载和外力可归纳为永久荷载、可变荷载和（）三类。
A.车辆荷载
B.人群荷载
C.汽车制动力
D.偶然荷载
参考答案：D
电动机的自起动
—Is there any hope of saving his life?
—His injuries are extremely serious, but he’s expected to ____.
A．pull in
B．pull through
C．pull up
D．pull over
