宾语从句和定语从句最主要是在定语从句中也可以用that宾语从句也可以.when and where 都可以.比如这个例子

宾语从句和定语从句
最主要是在定语从句中也可以用that宾语从句也可以.when and where 都可以.比如这个例子：It was at 5 o'clock when you should do your homework 为什么这里用when而不用that!
为了让各位更好的解答,我在总结一下以上的问题：
1：请解释下在什么情况下用定语和宾语从句（最好贴上一两个例子是对比的）和当that 用于定语和宾语从句的情况下不同的区别
2：再呢是解答我上述所说的问题.
3：当修饰一个地点的从句里,用where还是用that
--最主要还是第一个问题.
It was 5 o'clock when you should do your homework .如果去掉at 的话，那还是选when还是that呢？

（1）句子的组成部分,包括主语、谓语、宾语、定语、补语、状语、表语七种
定语就是修饰主语,宾语等成分的词语也可以是句子,那就是定语从句.定语用于描述名词,代词,短语或从句的性质,特征范围等情况的词叫做定语,定语可以由名词,形容词和起名词和形容词作用的词,短语担任.如果定语是单个词,定语放在被修饰词的前面,如果是词组,定语放在被修饰词的后面.
比如说蓝蓝的天.蓝蓝的就是定语.
He is the good man.good就是定语修饰man
he is the man who helped the teacher.who helped the teacher.就是定语从句
宾语一般是介词或者动词后面的词语,句子就是宾语从句.宾语是动作的对象或承受者,常位于及物动词或介词后面.宾语可由名词、代词、数词、名词化的形容词、不定式、动名词、宾语从句等来担任.
比如他是学生.学生就是宾语.
he is a student.a student就是宾语
He said that he would go to Shanghai.that he would go to Shanghai.
就是宾语从句
定语从句是指有先行词的从句
引导词为that which who whom where when as等
根据先行词在从句中充当的成分不同选择引导词疑问代词、疑问副词都是定语从句的引导词.
从句缺少主语,宾语,表语用疑问代词
缺少其他用疑问副词
例句：做宾语we often think of the days____we spent together on the island.
A when
B which
C in which
D during which
选B the days在从句中做宾语 用which
做状语He has left Beijing,____a meeting is to be held.
A when
B where
C as
D which
选B
Beijing 在从句中做地点状语 原句为He has left Beijing.In beijing a meeting is to be held.
做主语His father died last year,____made it impossible for him to go abroad.
A when
B which
C as
D that
选B 从句中made缺少主语,这是非限制性定语从句不能that 所以选which
注意：定语从句中不能用what引导从句
that引导的定语从句充当主语 宾语 表语成分
但是对于非限制性定语从句中,一般是跟在逗号后面的从句不能用that引导
可以选择as which who whom whose 等
宾语从句：及物动词,形容词和介词后加宾语从句作其宾语.
宾语从句时态与主句相呼应,但宾语从句表示的是客观真理或普遍现象除外The teacher told us that the earth moves around the sun.
宾语从句中that不做任何成分.也就是说that所引导的从句本身是完整的
（2）you should do your homework这个句子完整,那就是缺少时间状语,所以用 It was at 5 o'clock when .when修饰时间状语at 5 o'clock.我的理解
（3）当修饰一个地点的从句里,用where还是用that
应该看where|that前面的地点,也就是先行词在从句中什么成分
比如定语从句中地点在从句中做地点状语用where
如果做主语.宾语.表语无疑是用that啦.