句子中的 as on that of 是个什么使用方法(as 引导的是什么从句)

原句：

There must be few questions on which responsible opinion is so utterly divided as on that of how much sleep we ought to have.

主如果对这个as on that of 有点懵，不太理解。

that是替代词，替代the question. as从句省略了主语responsible opinion 和 系词 is，只保留了主语的定语 on the question of how much sleep we ought to have.  这个句子是用比较级形式表示最高级意义.nothing is so... as A.整个句子的意思是：A is the most on all things. 即大家需要多少睡眠时间，关于这个问题大家的看法的分歧是最大的。没什么问题大家的看法分歧有这个问题的分歧大。