燃烧的类型分为（）、（）、（）、（）四种。
参考答案：闪燃、着火、自燃、爆燃
Last year, I _______ ride a bike, but now I _______. I go to school by bike now.[ ]
A. couldn't, can
B. could,can't
C. couldn't, could
D. couldn't, can't
质量控制的活动分为哪几个阶段？
