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

問題詳情：

 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

知識點：動詞時態與語態

題型：選擇題