一道逻辑题目，大家帮忙看一下

Which of the following most logicallu completes the argument?

Yorco and Zoreth are two corporations that employ large numbers of full-time workers who are paid by the hour ,Publicly available records indicate that Yorco employs roughly the same number of
            such hourly wage  workers as Zortech does but spends a far higher total sum per year on wages for such workers .Therefore ,hourly wages must be higher ,on average ,at Yorco than at Zortech,since:

A:Zortech spends a higher total sum per year than Yorco does to provide its hourly wage workers with benefits other than wages

B:the work performed by hourly wage workers at  Zortech does not require a significantly higher level of skill than the work performed by hourly wage workers at Yorco does

C:the proporation of all company employees who are hourly wage workers is significantly greater at Yorco than it is at Zortech

D overtime work ,which is paid at a substantiallly higher rate than work done during the regular work week ,is rare at both Y and Z

答案是d，我不懂，红色部分和蓝色部分指的是同一类的人吗？