英语：九年级第九单元When was it invented?

被动语态（一般现在时）　　主动语态变被动语态时,主动语态句中的宾语变成被动语态句中的主语,主动语态句中的主语成为被动语态句中的动作的发出者。　　被动语态的口诀 　　一般现、过用be done,be有人称、时、数变。　　完成时态have(has) done,被动将been加中间。　　一般将来shall (will) do,被动变do为be done。　　将来进行无被动,shall (will) be doing,　　现在完成进行同,have (has) been doing。　　现、过进行be doing,被动be加being done。　　情、助、有、是妥安排,一律随新主语变。　　否定助后加not,疑问一助置主前。　　主语恰是疑问词,直陈语序主在前。　　一般情助加be done,双宾多将间宾变。　　复合宾语宾变主,宾补、主补相应变。　　第二句"be有人称、时、数变"即be有人称、时态和单、复数的变化。"情助"是指情态动词和助动词must,may,can,shall,will等一律随新主语(多是主动句中的宾语)来变化。"疑问一助置主前"是说有两个助动词的话,应把主语放在第一助动词之后或把第一助动词置于主语之前。下面详细举例说明之。　　一般现、过用be done,be有人称、时、数变 　　例：1、主动：The children gave the foreign guests a warm welcome。　　被动：The foreign guests were given a warm welcome by the children。　　孩子们热烈地欢迎外宾。　　2、主动：People regard him as brilliant。　　被动：He is regarded as brilliant by people。　　人们认为他很有才华。　　以上两例都是一般时态用be done的例子,be有人称、时、数变,第三人称foreign friends是复数,时态一般过去时,所以"be done"就是were given,而People regard him as brilliant一句,被动后的"be done"就变成单数第三人称is regarded的形式了。　　完成时态have done,被动将been加中间。　　(过去完成时had done也包括在内)。　　例：1、主动：We have studied English for 3 years off and on at the spare-time school。　　被动：English has been studied for 3 by us years off and on at the spare-time school。(have随新主语变为has) 　　我们已经在夜校里断断续续地学了三年英语了。　　2、主动:They had produced 100 tractors by the end of last year。　　被动:100 tractors had been produced by the end of last year。　　到去年年底我们已生产出一百台拖拉机。　　3、主动：They have set up a power station in their home town。　　被动：A power station has been set up in their home town。　　他们的家乡建立了一座发电站。　　4、主动：They have warned us to be careful of rats。　　被动：We have been warned to be careful of rats。　　他们已提醒我们要注意老鼠。　　5、主动：People have piled plastic bags full of rubbish in streets。　　被动:Plastic bags full of rubbish have been piled in streets。　　人们把装满垃圾的塑料袋子堆放在街上。　　6、主动：We have used nuclear energy to produce electricity。　　被动：Nuclear energy has been used to produce electricity。　　核能已用来发电。　　7、主动：No one has ever beaten him at tennis。　　被动：He has never been beaten at tennis。　　就网球来说还没有人是他的对手。　　(No one涉及到全否定和部分否定问题,见否定一讲) 　　过去完成时也是一样：　　主动:Somebody had cleaned my shoes。　　被动:My shoes had been cleaned by somebody。　　有人早已把我的鞋子擦了。　　一般将来shall (will) do,被动变do为be done 　　即由shall do或will do变为shall done或will be done。　　例：主动:We shall build several big modern power plants in our city next year。　　被动：Several big modern power plants will be built in our city next year。　　过年我市将建立几座大型现代化的发电厂。　　(shall do中的shall要随新主语变为will,do为be done。) 　　被动句中的by引出的宾语,一般说来,如果是人称代词你、我、他等,均可省略,someone no one不由by来引出。如果是名词不能省略,但当今英语也都可省略了。　　make。。。come true 使……成为事实; come true做宾补(见感使动词口诀)。　　但如果是一般过去将来时如何处理呢?请记下面口诀：　　一般过去将来时,过去某时将发生。　　主动should (would) do,被动be done代原形。　　将来进行无被动,现在完成进行同。