— My father _____ Shanghai with my grandparents.

— Really? _____ will they come back? [ ]

A. has been to; How soon

B. has gone to; How soon

C. has been to; How long

D. has gone to; How long

通过常规管理足以保证其安全性、有效性的医疗器械属

A．第一类
B．第二类
C．第三类
D．基本质量特征
E．质量保证