如图所示是一交流电压随时间变化的图象，此交流的有效值为____ V．

我国东北地区有辽阔的土地、浩瀚的森林。早在春秋战国时期，就吸引黄河中下游地区人口向这里迁移和流动，尤以山东人最多。东北地区俗称“关东”，人们便把不顾政府禁令，来此谋生的人口迁入现象，称为“闯关东”。直到1978年，黑龙江省农民的人均纯收入还比山东省高出2/3。改革开放以来，山东省经济增长迅速，山东省农民人均纯收入超过黑龙江省，由此导致了两地之间人口迁移方向的完全反转，出现了“雁南飞”现象。根据上述材料，回答下列各题。

《论语》云：“管仲相桓公，霸诸侯，一匡天下．”这则材料反映了什么历史事实（    ）

    Mr. Smith ____ in a police station for 42 years and he will retire this autumn. He tried to work hard in his life but he wasn't lucky enough ____even a thief.

    Last weekend, Mr. Smith ____ to buy some sugar in a shop. When he got into the shop, he suddenly saw a young man get some money from a woman's bag and walk away. He ran to the thief and at the end of a blind alley(死胡同), the young thief ____by Mr. Smith.

    “Please give me a chance, sir,” said the thief. “I'll never do that again!”

    “But who can give me a chance?” said Mr. Smith. “I____ next month and this is the first time I've caught a thief!”