do you know how to do it 是宾语从句吗
do you know how to do it 不是宾语从句，是一个简单句，意思是你知道怎么做吗？
宾语从句是名词性从句的一种。在主从复合句中充当宾语，位于及物动词、介词或复合谓语之后的从句称为宾语从句。宾语从句分为三类：动词的宾语从句，介词的宾语从句和形容词的宾语从句。
宾语从句特点
宾语从句可以作及物动词、介词及形容词的宾语。
宾语从句的语序一律用陈述句语序。
连接词that引导宾语从句在句中无词义，不充当句子成份，多数情况下可以省略。
whether 和 if 都可引导宾语从句，但 whether后可紧跟or not；whether从句可作介词的宾语。
如果从句太长，可以用形式宾语it. 补充宾语从句在句子中起宾语作用的从句叫做宾语从句。
宾语从句的用法
that引导宾语从句无意义，不充当句子成分常省略。但下列情况除外：
①．介词宾语从句的that不能省略。
②． and连接的两个从句，两个从句的that不能省略。
He told me that he had two sons and that they both had gone to college.
③．在动词+it+宾语补足语+宾语从句结构中，that不省略。
I heard it said that he had gone abroad
We found it impossible that he could finish it in such a short time
Whether,if 引导宾语从句：两词可互换，但是下列情形除外：
①．whether从句中有or not
②．whether从句做介词宾语
Everything depends on whether you agree with us
许多带复合宾语的句子，宾语从句经常移到句子后部，而用it做形式宾语。结构是：
主语 + 动词 + it + 形容词/名词等宾语补足语 + 宾语从句
We think it wrong that he told a lie to everyone.
①．宾语从句的语序要用陈述句语序。
False: He is wondering when can he finish this difficult job.
Right: He is wondering when he can finish this difficult job.
②. 有时候可以用it 作形式宾语，而把真正的宾语从句放在后面。
Bad: I thought that he could finish this job in just two hours impossible.
Good: I thought it impossible that he could finish this job in just two hours.
③. 带有宾语从句的复合句的否定形式一般是否定主句。
Bad: I think he doesn’t like the English teacher.
Good: I don’t think he likes the English teacher.
④. 主句一般过去时态，从句也要用过去时态；具体细节请看第一部分。
False: He wanted to know why he is crying in the corner.
Right: He wanted to know why he was crying in the corner.
