扩散通风
参考答案：
利用矿井空气中的自然扩散运动，对局部地点进行通风的方式。
— What a beautiful watch! Is it new?
— No, I have _____ it for 2 years. [ ]
A. had
B. sold
C. borrowed
D. bought
煅烧的最高温度是多少度？
