逻辑实在是差，这题不太明白是怎么回事~~谢谢大家啦
Which of the following most logically completes the argument?
Yorco and Zortech are two corporations that employ large numbers of fulltime workers who are paid by the hour. 
ublicly 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
答案是D， 实在是不明白，这个怎么能用来解释说Y的比Z的高？？