氧化物有哪两个生长阶段?
参考答案:
化学反应控制阶段和扩散控制阶段
The girls ______ to swim last month and they can swim very well now. [ ]
A. are taught
B. were taught
C. have taught
D. taught
燃烧具备可燃物,助燃物就可以了。