It's impolite to cut in line when you _______ a bus at the bus stop.
A:ask for
B:look for
C:care for
D:wait for
如图将图电磁铁连入你设计的电路中(在虚线方框内完成),要求:
量一量图中线段PA、PB、PC、PD的长度,你能发现什么?