下列物品中，通常情况下属于导体的是[ ]
A.布笔袋
B.铅笔芯
C.橡皮擦
D.塑料尺
答案：B
Jack's father is so ____________, because Jack failed the math test.[ ]
A. angry
B. bored
颈椎椎管前后径的正常下限是()
A．15mm
B．14mm
C．13mm
D．12mm
E．11mm
