采用比例画法绘制螺栓连接，若螺栓公称直径为d，则螺栓头部正六边形外接圆直径约为（），螺纹长度约为（），螺栓头部厚度约为（）。

The following information relates to Question 7 and 8. ...

单项选择题The following information relates to Question 7 and 8. A company operating a standard costing system has the following direct labour standards per unit for one of its products: 4 hours at $12.50 per hour Last month when 2,195 units of the product were manufactured, the actual direct labour cost for the 9,200 hours worked was $110,750. What was the direct labour rate variance for last month?
A、$4,250 favourable
B、$4,250 adverse
C、$5,250 favourable
D、$5,250 adverse

生物除磷过程中不需要提供有机碳源。

判断题生物除磷过程中不需要提供有机碳源。

粉路图中，2S表示第2道尾磨。

未知题型粉路图中，2S表示第2道尾磨。