A new bus service to Tianjin Airport started to operate two months ago.
A. normal
B. usual
C. regular
D. mon
网友回答
A. normal
B. usual
(答案→)C. regular
D. mon
解析：normal正常的( normal temperature, return to normal); usual通常的（usual time, usual restaurant); regular定时/期的，有规律的（regular breathing; a regular bus service ）; mon一般的，常见的（mon sense, mon names）。