木炭在氧气中燃烧时发出白光。
参考答案:对
The Smiths are at home. Bill is listening to the music. Mother said to her son,
"Bill, Would you please _____ a little, your baby brother is sleeping." [ ]
A. turn off it
B. turn it off
C. turn down it
D. turn it down
为了保证发动机的正常工作和减少()损失,要求连杆在尽可能小的重量下,达到一定的刚度和强度,所以连杆的杆身大多制成“工”字形断面。
A、热量
B、能量
C、燃料
D、摩擦