4C

→GT: The hotel requires guests when going out to give the room key to the receptionist, B is still correct because the guest can keep the room key with them if there is no one at the reception, but it is easy for the guest to lose it, so C is most satisfying

5B

→GT: in answer A: guests can access anything on the phone as long as they do not make or receive calls. In answer C: guests can answer the phone in empty places in the hospital such as toilets as long as it does not affect doctors and patients. In answer B, if it's an emergency, tell the hospital staff that you want to answer the phone so they know and don't have any regrets.