【单选题】The main duty of a __________ to maintain and repair facilities in the guestroom.
【单选题】吸附指示剂因吸附到沉淀上的颜色与其在溶液中的颜色( )而指示滴定终点。
【单选题】The main duty of a __________ to clean the guestroom.
【单选题】The main duty of a __________ to take care of the guests’ luggage.