中压高温状态下，宜选用非金属与金属组合垫片或（）
A、金属垫片
B、非金属垫片
C、橡胶垫片
D、自紧式垫片
参考答案：A
—How did you manage to get such a nice old painting?
—Quite _____. [ ]
A. by accidents
B. by a chance
C. by accident
D. by incident
