As a teacher, I seldom give my students so difficult a problem ________ they can not work out.[ ]

A. that       

B. if          

C. in order that

D. as

下列不是交车环节令顾客欣喜的服务流程是（）

A、当顾客的面去除防污四件套

B、提醒顾客下次保养时间和公里数

C、提醒CSI回访时间

D、不需要询问客户对服务的满意程度