這篇關于初二英語下冊第六單元知識點，是

　　被動語態(tài)：主語（動作承受者）←謂語（be+動詞過去分詞）←賓語（動作發(fā)出者）He wrote the letter. →The letter was written by him.4）主動句變被動句的基本句式：a) 主：主語+助動詞（情態(tài)動詞）+謂語+賓語被：主語（原賓語）+助動詞（情態(tài)動詞）+be+動詞過去分詞+by+原主語如，We will help him.→He will be helped by us.主：主語+動詞短語+賓語被：主語（圓賓語）+be+動詞短語的過去分詞+by+原主語如，They looked after the babies.→The babies were looked after by them.主：主語+謂語+間接賓語+直接賓語被：主語（間接賓語）+be+動詞過去分詞+原直接賓語主語（直接賓語））+be+動詞過去分詞+to(for)+原間接賓語+（by+原主語）如，We gave him some magazines.→He was given some magazines.Some magazines were given to him by us.【注意】一般將主動句中表示人的間接賓語變?yōu)楸粍泳渲械闹髡Z。主：主語+謂語+賓語+賓語補足語被：主語（原賓語）+be+過去分詞+原賓語補足語如，They elected him their monitor.→He was elected their monitor.【注意】如果主動句中賓語補足語是不帶to的不定式，變成被動語態(tài)后一般要加to.I saw him go to the church.→He was seen to go to the church.【擴展】一般在以下幾種情形時，需要使用被動語態(tài)。不知道動作的執(zhí)行者，只知道動作的承受者時。When we got there, the room had been cleaned already.不必要說出或出于禮貌不便說出動作的執(zhí)行者時。I was told that you were not honest enough.３）有必要突出或強調(diào)動作的承受者時。You were asked to answer this question.16.if與whether:if和whether均可用于賓語從句中，意為“是否”；if用于條件句中，表示“如果”，不能和or連用；whether常與or連用，表示兩種條件或情況?！緮U展】if not..如果不是…,表示驚訝或憎惡等情緒；if only意為“若…那就好了，我多么希望…”相當于how I wish；only..if..意為“決不…除非…”If it hadn’t been for the doctor’s care, I should not be speaking to you now.如果不是醫(yī)生的照顧，我現(xiàn)在就不會和你說話了。If only he arrives in time!若他及時到達就好了。I’ll only come if you promise me that you won’t invite Henry.除非你答應不請亨利，否則我不會來。