发动机工作时，化油器出现“回火”现象，原因可能是（）。
A、可燃混合气过浓
B、可燃混合气过稀
C、化油器浮子室内油面过高
D、主量孔开度过大
参考答案：B
—_____ that makes her different from the other students?
—Honesty, hardwork and, I suppose, a bit of imagination.[ ]
A. What do you know
B. What do you think it is
C. How do you believe
D. How come that
什么是混合（上网成形器）？
