Which Worker Is Most Likely Going to Have the Greatest

 Which worker is most likely going to have the greatest difficulty with disruptions in their circadian rhythms? 

A) John, who works from 3PM to midnight five nights a week
B) Joan, who works from midnight to 8AM five nights a week
C) Bill, who works from 8 AM to 4 PM seven days a week
D) Becky, who works from midnight to 8 AM on the weekends and 8 AM to 4 PM on Tuesday, Wednesday, and Thursday