—Is your grandma better now?    

—Er, in fact, things are getting ________. Doctors are trying their best.[ ]

A. bad         

B. ill            

C. worst        

D. worse

MAP的主要功能是在各个实体之间交换与电路无关的数据和指令，从而支持移动用户漫游，切换和用户鉴权等网络功能。