than 的用法

下面的文字摘自“英语语法网”，可供你参考：
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有时可引导一个从句并在从句中充当句子成分(主语、宾语、表语)，为便于理解，有时可视为than后省略了what：

We don’t want to do more than is necessary. 我们不想做不必要的事情。

The pain was almost more than he could bear. 这样的痛苦几乎使他受不了。

She’s not a very good manager she always spends more money than she earns. 她不大会理财——总是入不敷出。

Life here is much easier than it used to be. 如今在此地生活比起从前可舒服多了。

比较下面一句，than后的expected为省略结构：

He returned three days earlier than (he was) expected. 他回来得比预料的要早三天。

C.has been put in

因为requires more money 是从句，后面一定跟句子

这里省略了 that

The experiment requires more money than that has been put in