( )是对外贸易发展的核心。

A．加强和贸易伙伴的合作

B．国际竞争力

C．保护幼稚产业

D．各贸易国间的平等地位

The Education Department says that school safety has set off alarm bells with frequent reports of serious

accidents ________ students got injured or killed.[ ]

A．after which  

B．in which

C．by which  

D．for which