Beijing         a lot in the past ten years. Now it has become one of the biggest

modern          in the world.

   [ ]

A. changes, cities      

B. changed ;city

C. has changed; cities    

D. had changed; cities

为人民服务，包含着社会主义道德不同层次的要求，体现着社会主义职业道德建设的（）要求与广泛性要求的统一。