对密封容器进行气密性试验时，应先通入低于工作压力()。

A. 生态持续发展
B. 文化持续发展
C. 经济持续发展
D. 社会持续发展

A. 全面管治权
B. 实质管治权
C. 外交主导权
D. 人事主导权

A．Sophia made her Carnegie Hallpiano debut at 14.
B．Lulu led a prominent youth orchestra.
C．Both girls are humorless robots with terrible dress sense.
D．Both girls are never allowed to watch television, play computer games or go to sleepovers.