把20米长的钢筋，锯成每段一样长的小段，共锯9次，每段长（ ）米，如果锯成两段需1分钟，锯成9段共需（ ）分钟。
2；8
---Why are you so late?
---I was on the way when it to me that I had left my book home,so I had to fetch it.[ ]
A. occurred
B. hit
C. happened
D. reminded
好氧微生物分解水中有机物可分为两个阶段，即（）和（）。
