It is easy to do.为什么do后面没有it 而Please show me how to do it有it

Would you please tell me what to do it 对吗,how to do 后面可以接it吗 show us how to do it是什么意思 Let me show you how to do it how to do it? it is very easy ,try to do it y___ ( )let me show you a.what to do it b.which to do it c.how to it is easy to do sth.跟it easy to do sth. how to do it then it is difficult to do 与 it is no easy thing to do 区别 it is ___(easy) to say than to do i will show you how to do it It is easy to do A,but you'll find it difficult to do B.