设备及管道安装致密性试验包括（）等。
A．水压试验
B．机械强度试验
C．气压试验
D．气密性试验
参考答案：A, C, D
Fu Mingxia ______ the Sydney Olympic Games, where she ______ all the other competitors and
got the gold medal in the women's 10-metre platform. [ ]
A. participated in; beat
B. participated in; won
C. participated; beat
D. participated; won
已知圆C：（x-3）2+（y-4）2=4和直线l：x+2y+2=0，直线m，n都经过圆C外定点A（1，0）．
（Ⅰ）若直线m与圆C相切，求直线m的方程；
（Ⅱ）若直线n与圆C相交于P，Q两点，与l交于N点，且线段PQ的中点为M，求证：|AM|•|AN|为定值．
