预热阀分别有（）三个位置。
参考答案：旁通、最小加热、最大加热
英语问答。
( ) 1. What's your favourite clothes? A. I like to play ping-pong.
( ) 2. What's your favourite food? B. Yellow.
( ) 3. What's your favourite school work? C. Write stories.
( ) 4. What's your favourite colour? D. Shirts and shorts.
( ) 5. What do you like to do? E. Sandwich and milk.
机械通风的方式有（）、（）、（）。
