术后尿路感染发生的相关因素不包括（）

A.使用免疫抑制药

B.机体抵抗力下降

C.留置导尿

D.会阴部不清洁

E.长时间卧床

—With 3G mobile phones, people can even see each other as they talk.       

—Really? Would you show me        it, please?       [ ]

A. how to use    

B. when to use    

C. where to use    

D. what to use