家庭电路的供电线有两根，有一条在户外就已经和大地相连，叫做______，另一条叫做______，俗称火线．使用试电笔时，用手指按住笔卡，笔尖接触______时，测电笔的氖管就会发光．
家庭电路中有两条进户线，有一条在户外就已经和大地相连，叫零线．另一条叫端线，俗称火线．
手接触测电笔的笔尾金属体，笔尖金属体接触导线，氖管发光时，接触的导线是火线．
故答案为：零线；端线；火线．
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| There was a boy who was sent by his parents to a boarding school (寄宿学校)．__1__ being sent away，this boy was the__2__student in his class.He was at the top in every__3__ always with high marks. But the boy changed after__4__home and attending the boarding school.His grades started __5__.He hated being in a__6__.He was lonely all the time.And there were especially dark times when he__7__committing suicide (自杀)．All of this was because he felt__8__and no one loved him.His parents started__9__about the boy.But they even did not know what was __10__with him.So his dad decided to travel to the boarding school and__11__him. They sat on the bank of the lake near the school.The father started asking him some casual questions about his classes，teachers and__12__.After some time his dad said，“Do you know，son，why I am here today？” The boy answered back，“To__13__my grades？” “No，no，”his dad replied.“I am here to tell you that you are the most__14__person for me.I want to see you__15__.I don’t care about grades.I care about you.I care about your happiness.YOU ARE MY LIFE.” These words__16__the boy’s eyes to be filled with tears.He__17__his dad.They didn’t say anything to each other for a long time. Now the boy had__18__he wanted.He knew there was someone on this earth who cared for him deeply.He__19__the world to someone.And today this young man is in college at the top of his class and no one has ever seen him__20__！ | |||
| ( )1．A.After ( )2．A.hardest ( )3．A.exam ( )4．A.coming ( )5．A.rising ( )6．A.group ( )7．A.led to ( )8．A.worthless ( )9．A.caring ( )10．A.crazy ( )11．A.talk with ( )12．A.family ( )13．A.realize ( )14．A.outstanding ( )15．A.happy ( )16．A.caused ( )17．A.answered ( )18．A.nothing ( )19．A.showed ( )20．A.sad | B．Before B．naughtiest B．activity B．returning B．increasing B．term B．felt like B．careless B．turning B．true B．listen to B．friends B．analyze B．important B．excellent B．wanted B．ignored B．something B．meant B．angry | C．When C．brightest C．game C．leaving C．reducing C．company C．thought back C．concerned C．worrying C．possible C．tell to C．study C．check C．famous C．interested C．encouraged C．hated C．everything C．intended C．pleasant | D．While D．dullest D．class D．reaching D．dropping D．party D．looked for D．annoyed D．speaking D．wrong D．care about D．grades D．test D．familiar D．satisfied D．forced D．hugged D．anything D．expressed D．joyful |