裂解汽油加氢装置采用水封槽水封是为了保持BTX（脱碳九）塔的真空度。
参考答案：对
Miss Li _______ as a secretary for five years in the company, and now she is general manager of it.
A．serves
B．served
C．has served
D．had served
在国际服务贸易领域中的壁垒中，广泛使用的贸易壁垒是( )
A．绿色壁垒 B．《服务贸易总协定》C．非关税壁垒 D．关税壁垒
