Please explain The Object Clause to me thoroughly,thanks.

Please explain The Object Clause to me thoroughly,thanks.

中学英语宾语从句语法讲解
[宾语从句歌诀]
宾语从句三姊妹,that,if/whether,wh-/how展风采.
展风采有三关,引导词、语序、时态在把关.
主从时态要一致,陈述语序永不变.
陈述请你选that,疑问需用if/whether连.
特殊问句作宾从,原来问词不用换.
三关过后莫得意,人称、标点需注意.
留意变脸的if/when,从句的简化记心间.
[歌诀解码]
一、三姊妹
宾语从句根据引导词的不同可分为三种类型：
1.由that引导的宾语从句.如：
We knew （that）we should learn from each other.
2.由if/whether引导的宾语从句.如：
Please tell me if/whether you have been to America.
3.由who,where,how等连接代词或连接副词引导的宾语从句.如：
Can you tell me how I can get to the nearest post office?
二、三关
1.引导词关
如果从句是陈述句,引导词用that（that在口语或非正式文体中常省略）；如果从句是一般疑问句,引导词用if/whether；如果从句是特殊疑问句,引导词用由疑问词转换而来的疑问代词/副词.
2.语序关
①陈述句变为宾语从句,语序不变,即仍用陈述语序.如：
He is an honest boy.The teacher said.→The teacher said（that）he was an honest boy.
②一般疑问句和特殊疑问句变为宾语从句,语序变为陈述语序.如：
Does he work hard?I wonder.→I wonder if/whether he works hard.
When did he leave?I don’t know.→I don’t know when he left.
3.时态关
①如果主句是现在的时态,从句的时态可根据实际情况而定.如：
I have heard（that）he will come back next week.
②如果主句是过去的某种时态,那么从句的时态一定要用过去的某种时态.如：
He said（that）there were no classes yesterday.
注意：如果宾语从句表述的是客观真理、自然现象等时,不管主句是什么时态,从句都要用一般现在时.如：
He said that light travels much faster than sound.
三、人称的变化和标点的使用
1.从句的主语如果是第一人称,变为宾语从句则与主句的主语一致；如果是第二人称,则与主句的宾语一致；如果是第三人称,不用变化.如：
“May I use your knife?”He asked me.→He asked me if he might use my knife.
“Do you know her telephone number?”He asked me.→He asked me if I know her telephone number.
2.宾语从句的标点均由主句决定.主句是陈述句,用句号；主句是疑问句,用问号.如：
Who will give us a talk?I don’t know.→I don’t know who will give us a talk.
Do you know?Where does he live?→Do you know where he lives?
四、两副面孔
if和when既能引导时间状语从句,又能引导宾语从句.因此,遇到它们就要认真分析一下,它们究竟属于“两副面孔”的哪一副.如：
If it rains tomorrow,I won’t come.（时间状语从句）
I don’t know if it will rain tomorrow.（宾语从句）
五、从句的简化
1.当主句谓语动词是find,see,watch,hear等感官动词时,从句常简化为“宾语＋宾补”结构,宾补为不带to的不定式或V-ing形式.如：
She found that the wallet lay/was lying on the ground.→She found the wallet lie/lying on the ground.
2.当主句谓语动词是hope,wish,decide,forget,plan,agree等,且主句主语与从句主语相同时,从句可简化为不定式结构.如：
She agreed that she could help me with my maths.→She agreed to help me with my maths.
3.在连接代词/副词引导的宾语从句中,当从句主语与主句主语或间接宾语一致时,宾语从句可简化为“连接代词/副词＋不定式”结构.如：
Can you tell me how I can get to the station?→Can you tell me how to get to the station?