The book which I need it isn't in my schoolbag.All that I could do is to send him to school.Dr.Stone,who has come for a visit to China ,arrived in Beijing yesterday.This factory will not take anyone of that eyesight is weak.哪里有错为什么要去掉it,那which I need it改成what I need可以吗不用that，那用which/what/the thing为什么用whose

The book which I need it isn't in my schoolbag.
去掉it.
因为主语是the book,不能再用一个主语了.
不能用what,是定语从句,而不是主语或宾语从句.如果说A book is what I need,就要用what.
All that I could do is to send him to school.
去掉that.
All后面的定语从句只能用that,而且一般是省略掉的.
Dr.Stone,who has come for a visit to China ,arrived in Beijing yesterday.
无错.
This factory will not take anyone of that eyesight is weak.
of that改为whose.
工厂不会要任何弱视力的人.
视力和anyone的关系肯定是从属关系,所以要用whose来引导定语从句.