Beijingwasunderan“orange”smogalertonFeb.24,whichmarkst...

问题详情：

 Beijing was under an “orange” smog alert on Feb. 24, which marks the first time the second-highest warning level of a new system introduced last year          .

A. raised        B. has been raised        C. rose        D. has risen

【回答】

B

知识点：动词时态与语态

题型：选择题