货叉的垂直段用以和（）相连接。
参考答案：叉架
已知⊙A与⊙B相切，两圆的圆心距为5，⊙A的半径为2，则⊙B的半径为______．
Can you tell me your _____ of success?
There is no easy way to learn English well. Just work hard.[ ]
A. duty
B. trouble
C. secret
D. rule
