下列哪些道岔以正线开通位置作为定位。（）
A.引向安全线的道岔
B.单线车站正线进站道岔
C.双线车站正线进站道岔
D.区间内正线道岔
参考答案：C, D
—Are you going to but a new camera?
—Yes. But there are so many cameras that I can’t decide______________.
A. how to use B. where to sell C. which to buy
所有运行人员对防误装置应做到哪"四懂三会"？
