在某些情况下，电线有颜色编码，这些应该在线路图上标明。
A.These must be shown on the wiring diagram under some specific conditions and wires are color coded. B.Wires are coded in color in certain condition, and these should be marked on the wiring diagram. C.In some cases, wires are color coded, and these should be indicated on the wiring diagram.正确答案C
