Which of the following most logically completes the argument?

Yorco and Zortech 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 proportion 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 substantially higher rate than work done during the regular work week, is rare at both Yorco and Zortech

E.    the highest hourly wages paid at Yorco are higher than the highest hourly wages paid at Zortech

答案 为什么是 D

我选 b

解释题，不需要充分性。

sum = number of workers * total hour

和skills(B)无关。