集中式供水的管道埋设时，应注意：饮用水管道与污水管交叉时，饮

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问题单项选择题

集中式供水的管道埋设时，应注意：饮用水管道与污水管交叉时，饮用水管道应在上面，且间距不小于（）

A．0.1m

B．0.4m

C．0.5m

D．1.0m

E．1.5m

答案

参考答案：B

解析：

集中式供水的管道埋设时，应注意：饮用水管道与污水管交叉时，饮用水管道应在上面，且间距不小于0.4m；饮用水管道与污水管平行时，垂直距离应有0.5m，水平距离不小于1.5～3m。

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完形填空。
Peter and James were brothers. One afternoon ___1____ the lessons were over, they stayed in school to help their teacher. They___ 2__ for an hour. Then the teacher said, "Thank you, boys. We will finish the work tomorrow. Now you must go home." When the boys ___3_____ home, it was seven o'clock. There was light inside their house and the door was ____4____. They could see a man inside, too. "Who can it be?" thought Peter. "Father and Mother have gone shopping. They won't be home ____5____ eight o'clock." When the _____6____ man saw Peter, he smiled and said, "Come in! You don't know me, but I'm your ___ 7 ___ friend. He asked me to fetch some money for him." The man did not see James. Peter went inside and began talking to the man but James did not. He quietly but quickly ran off to call the police. He soon found a policeman and _____8____ him back to their home. The man was still there, but when he saw the policeman, he tried to run off. The policeman _____9____ him and held his arm. Just then Mr. and Mrs. Baker, the boys' parents ______10______. "No!" said Baker. "I don't know him. He must be a thief. I am glad you have caught him."
( )1. A. if ( )2. A. studied ( )3. A. arrived in ( )4. A. open ( )5. A. at ( )6. A. away ( )7. A. father ( )8. A. brought ( )9. A. stoped ( )10.A. returned	B. when B. worked B. went to B. opened B. since B. out B. fathers B. bring B. stopped B. come	C. before C. stayed C. got to C. opening C. until C. outside C. father's C. take C. catch C. arrive	D. until D. watched D. reached D. close D. after D. inside D. brother's D. caught D. saw D. reached

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多项选择题

开关电源功率回路与控制回路常用的电气隔离方案有（）

A、变压器隔离

B、运放隔离

C、光耦隔离

D、二极管隔离

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