Which of the following must be available 24 hours a day A. The restaurant. B. The bar. C. Room service. D. The laundry. E. All of the above.

I think Room Service and Laundry 

IN A5 STAR HOTEL ROOM SERVICE ONLY. BUT IT CAN BE A DELICATE CHOICE OF WHAT TO OFFER FOR THIS SERVICE.  A FULL MENU WOULD BE SUPER DIFFICULT UNLESS YOU WANT TO ENGAGE IN AT LEAST2 PERSONS OF NIGHT SHIFT, KITCHEN AND SERVICE.

Nothing. For working  at night time-extra pay. Other people must have rest. I like commandant hours-then lights off and works finish.

What would you ask for at night ?  Rather than something to eat ...

room service must be available

 of course the answer is room service

All of the given is usefull for different job performers

peoples need the room service  in iny time

Room service of course without neglecting other services.