矿井通风难易程度为通风中等的其等积孔的值为（）m2。
A、小于1
B、1～2
C、大于2
D、大于4
参考答案：B
His letter, _____ to the wrong number, reached me late. [ ]
A. having been addressed
B. to have addressed
C. to have been addressed
D. being addressed
分析性程序最好是归在以下哪类
A．实质性测试。 B．控制测试。C．定性测试。 D．预算比较。
