装有一级易燃固体的车辆，距牵引的电力机车最少隔离（）辆。
A.2
B.1
C.3
D.4
参考答案：A
The conference has been held to discuss the effects of tourism _______ the wildlife in the area.
A．on
B．in
C．at
D．of
简述海洋生态环境被污染和破坏的事例。
