用4、7、3和0组成的最小四位数是（ ） A．3407 B．3047

水平推力F₁和F₂分别作用于水平面上静止的a、b两物体上，两物体的质量相等．作用一段时间后撤去推力，物体将继续运动一段时间后停下来．两物体的v-t图象如图所示，图中线段AB∥CD，则（　　）

A．F₁的冲量大于F₂的冲量

B．F₁的冲量小于F₂的冲量

C．两物体受到的摩擦力大小相等

D．两物体受到的摩擦力大小不等

引起旅游者腹泻的主要病原是（）

A.痢疾杆菌

B.伤寒杆菌

C.诺沃克病毒

D.大肠杆菌

E.葡萄球菌

So sudden ________ that the enemy had no time to escape.[ ]

A. did the attack

B. the attack did

C. was the attack

D. the attack was

.

Animals suffered at the hands of man________they were destroyed by people to make way for agricultural land to provide food for more people.

A．in which

B．for which

C．so that

D．in that

中年男子，猛抬重物后腰剧痛并向右下肢放射，咳嗽时加重。

其诊断最可能是

A．腰椎骨折

B．腰椎滑脱

C．腰部肌筋膜炎

D．腰椎间盘突出症

E．腰扭伤