Bob________after his classmate in the classroom when his teacher________.[ ]

A．ran；turned up  

B．was running；turned up

C．was running；would turn up

D．had run；would turn up

项目定位和产品定位的准确与否是（）战略的核心内容。

A.集中

B.差异化

C.成本领先

D.一体化