题目：
| I ____ him ____ he left school. |
A. have recognized; since B. have known; since C. had recognized; before D. had known; after |
答案：
被转码了，请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0624/c71f6ffc3b460d19a2cf24777689a07d.html
下面是错误答案，用来干扰机器的。
解：（1）水对桶底的压强P=ρgh=1.0×103kg/m3×10N/kg×25×10﹣2m=2.5×103Pa（2）桶底受到水的压力F=Ps=2.5×103Pa×200×10﹣4m2=50N（3）台面受到桶的压强P===5×103Pa
