One Reason That Night Shiftwork Has a Detrimental Effect on Circadian

One reason that night shiftwork has a detrimental effect on circadian rhythms is that

A) there isn't enough variability in the sleep schedules of night shiftworkers
B) the nature of night shiftwork is more physically taxing than other types of work typically done during the day
C) night shiftworkers often do not get enough sleep
D) night shiftworkers often go home in the morning daylight, which makes it difficult to reset their circadian clocks