题目

边长为a，b的长方形周长为12，面积为10，则a2b+ab2的值为（ ）A. 120 B. 60 C. 80 D. 40 答案：【答案】B【解析】直接利用提取公因式法分解因式，进而求出答案．解：∵边长为a，b的长方形周长为12，面积为10，∴a+b＝6，ab＝10，则a2b+ab2＝ab（a+b）＝10×6＝60．故选：B．Today there are policemen everywhere, but in 1700, London had no policemen at all. A few oldmen used to protect the city streets at night and they were not paid.In 1750, Henry Fielding started to pay a group of people to stop thieves. They were likepolicemen and were called "Bow Street Runners" because they worked near Bow Street.Fifty years later, there were 120 "Bow Street Runners", but London had become very big andneeded more policemen. So in 1829, London Police Force was started with 3,000 officers. Until1920 all the police in London were men.小题1:Who protected London in 1700?  (回答词数不超过4个)小题2:When was London Police Force started?  ( 回答词数不超过2个)小题3:Are all the London police men now?  (回答词数不超过1个)