充装系统使用的压力表，精度不应低于（）级，表盘直径不小于150mm。
A.1
B.1.6
C.2.5
D.2
参考答案：A
80. Last week, we had a meeting. I told the chairman that I couldn’t attend it for I had something important to do, but he insisted _____ my being present.
A．on
B．in
C．to
D．At
小儿开始更换恒牙的年龄范围是（）
A．2～3岁
B．4～5岁
C．6～7岁
D．8～9岁
E．10岁
