单选题During the period of&nbsp

问题补充：

单选题Duringtheperiodofrecentterroristactivities,people_____nottotouchanunattendedbag．A.had always been warnedB.were always being warnedC.are always warningD.always warned

答案：

B解析考查时态。这里用过去进行时表示过去某个时候经常性的动作。