1.This is （）difficult a problem for （）little boys to work ou

This is （so）difficult a problem for （such）little boys to work out
so +形容词+名词 so clever this boy
such +名词 such a clever boy
Not all of students go out for pleasure.表示不是所有学生,可以用some代替
All of students do not go out for pleasure 同上
None of students do not go out for pleasure这句话错了,应该是None of students go out for pleasure 表示全盘否定

This is （so）difficult a problem for （such）little boys to work out
Not all of students go out for pleasure。
All of students do not go out for pleasure
这两句都表示 并不是所有的学生外出就是为了娱乐
None o...

such，so
有区别None of students do not go out for pleasure，没有学生不出去玩的
应改为 None of students go out for pleasure