The main problem of the round-the-clock working system lies in ______.A．the inconveniences

The main problem of the round-the-clock working system lies in ______.

A．the inconveniences brought about to the workers by the introduction of automation

B．the disturbance of the daily life cycle of workers who have to change shifts too frequently

C．the fact that people working at night are often less effective

D．the fact that it is difficult to find a number of good night workers