句意：不管文书工作有多难，这名会计都要在明天中午前完成费用报告。

这里的 no matter how 用于引导让步状语从句（根据空格后的形容词 difficult 可知空格处应填副词 how）。又如：

I wash every day no matter how cold it is. 无论多冷，我每天都洗澡。

We’ll have to finish it, no matter how long it takes. 不管要花多长时间，我们都要完成它。

No matter how hard I worked, she was never satisfied. 无论我多么努力地工作，她从来没满意过。

He had to get the car fixed no matter how much it cost. 不管花多少钱，他也得把车修好。

I’ve never known him to put a foot wrong, no matter how delicate the issue. 不论问题多么棘手，我从没见他出过错。