因截面变化引起应力集中的可以是（）。
A.退刀槽
B.油孔
C.阶梯轴
D.以上都是
参考答案：D
Sanya is _____ the south of China.[ ]
A. in
B. on
C. to
D. at
In relation to the law of partnership, discuss the liability of a retired partner for the debts of the partnership incurred both before, and after, his retirement. (10 marks)
