直流母线应采用分段运行的方式，设置在两段直流母线之间联络开关，正常运行时开关处于断开位置。
参考答案：对
_______ a reply, he decided to write again.[ ]
A. Not receiving
B. Receiving not
C. Not having received
D. Having not received
肾脏平片，肾轮廓能显示的原因是（）
A.密度比周围组织高
B.密度比周围组织低
C.肾周围包有脂肪垫
D.肾脏内有尿液
E.肾脏血运丰富
