Password is a secret series of (69) that enables a user to access a file, computer, or program. On multi-user systems, each user must enter his or her password before the computer will respond to (70) . The password helps ensure that (71) users do not access the computer. In addition, data files and programs may require a password.

A．symbol

B．sign

C．characters

D．characteristic

哪种病人应慎用血管内碘对比剂（）

A.梗阻性黄疸

B.一侧肾积水

C.肺结核

D.氮质血症

E.HbsAg阳性