由于气管、支气管解剖结构特点，支气管扩张易发生于()
A．左侧支气管
B．右侧支气管
C．两下叶支气管
D．前段支气管
E．上叶支气管
参考答案：C
If the firefighters ________ in time, the fire would have resulted in many deaths in the hotel.
A．wouldn’t have arrived
B．hadn’t arrived
C．didn’t arrive
D．shouldn’t arrive
计算液体的流量是把流过断面的面积与该液体的最大流速相乘。
