求该英语选择题答案及原因(尤其是A.B两个选项) Beijing was under an 'or
求该英语选择题答案及原因(尤其是A.B两个选项) Beijing was under an 'or
求该英语选择题答案及原因(尤其是A.B两个选项)
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.has been raised
B.raised
C.has risen
D.rose