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

上消化道大出血的临床表现为大量呕血和便血，一般来说，呕血还是血取决于（）

A.出血部位

B.出血速度

C.年龄

D.出血速度和量

E.出血时间