导游讲解中，使用（）时，介绍背景知识或材料切不可离题万里。

A.悬念法

B.渗透法

C.类比法

D.情景法

My brother is really __________. He often works in his office far into the night. [ ]

A. open-minded  

B. hard-working

C. self-confident  

D. warm-hearted