You can hardly imagine the once clear canal _____ so seriously polluted that no fish can live in it. [ ]

A. have become  

B. having become  

C. to have become  

D. to become

行政合理原则的具体要求是：( )的行政行为在合法的范围内还必须合理。

A．行政机关

B．行政人员

C．行政领导

D．行政主体