Duty is a course of action that people   you to take by social customs , law or religion.

A．persuade

B．request

C．instruct

D．expect

支气管哮喘的肺功能异常，主要表现在（）

A.肺活量减少

B.最大通气量增加

C.第一秒钟用力呼气容积减少

D.弥散量下降

E.功能残气量减少