如何对压力容器进行气密性试验？
参考答案：
气密性试验的程序是缓慢升压到设计压力后保持30分钟，同时进行检查，气体温度应不低于5℃。
结构性碳水化合物
That George will marry Alice, ______ has not been announced yet, has spread around.
A．that
B．which
C．what
D．who
