------ How was your trip to Yungang Caves during your National Day holiday?

-------- Wonderfully! I’ve never had _______ one before．

A．a pleasant

B．a more pleasant

C．a most pleasant

D．the most pleasant

目前大容量高参数机组普遍采用的发电机冷却方式为（）。

A、水冷；

B、双水内冷；

C、油冷；

D、氢冷。