(2013·宁夏银川一中高三第四次考试)Each of the 400 people received from their boss ________ gift—“Who moved my cheese？”， ________ best­seller in the US, which helped them understand how to deal with changes in their lives and work.

A．the; /

B．a; /

C．a; a

D．the; a

纯净的半导体是一种有用的半导体。