“关注民生”是建设和谐社会的重要内容.为了广大市民的身体健康，锦州市目前已改进自来水的消毒方式，将以前利用Cl₂消毒方式改为利用Cl₂O消毒方式.请你指出Cl₂O中氯元素的化合价[ ]

A.+1

B.+2

C.-1

D.+3

______ seen such a magnificent city as Beijing.

A．I before never have

B．Never have before I

C．Never before have I

D．Before never have I