以销子能自由插入孔中的长度约占销子长度的（）为宜。
A.50%～55%
B.60%～65%
C.70%～75%
D.80%～85%
参考答案：D
It's time _____________ lunch.[ ]
A. have
B. to have
C. has
D. having
单组柱上式中压无功补偿装置常用经验安装位置如何确定？
