She had since been rushing off to the library a little more often than was strictly necessary for somebody who had no homework to do.

加下划线的部分省略了什么主语？

【翻译】从那以后，她就一直跑图书馆，只是比那些没有作业的人需要去图书馆，经常一些而已。

【分析】这是一个含有比较结构的复合句。主句部分含有often 的比较级：a little more often，than was strictly necessary for somebody who had no homework to do 是比较从句。关于than 是从属连词还是关系代词，目前有争论。

1. 认为than 是从属连词，那么就是引导比较状语从句。这样的话，was strictly necessary 缺少主语；

2. 认为than 是关系代词，本身既表示“比...”的意思，又作了was strictly necessary 的主语。

我认为：实际上，从句中的主语不是省略，而是由than 充当了，这个主语是无法添加上的！

关于than在从句中作主语的例句：

The question is more complicated than appears on the surface.

这个问题比表面看上去要复杂得多。

He never says more than is necessary.

他从不多说没有必要的话。（他从不说废话）

He often eats more than is good for his health.

他常常吃的饭量多于对身体有益的量。

The family spent more than is prudent or necessary.

该家庭花钱过多，超过了必要的限度。

It is not wise to be wiser than is necessary.

聪明过了头，就是不聪明。

The man drank a little more than was good for him.

那个人酒喝得过了量。

Always do more than is required of you.

凡事永远要超要求完成。

He offered more information than is needed.

他提供了多余的信息。