A: 拖拉机的履带
B: 切蛋器的钢丝
C:书 包的背带
D: 铁轨的路枕
The plane had already taken off. So he decided ________the G109 Train to Shanghai.
.
爸爸身高176____
小军身高1____
已知点 P1 的球坐标为4,π2,5π3 , p2 的柱坐标为2,π6,1 ,则|P1P2|= ( )