在市场经济体制下，资源的配置通过以下哪些机制来实现( )。

A．等价交换机制

B．竞争机制

C．信息机制

D．风险机制

By nine o'clock, all the Olympic torch bearers had reached the top of Mount Qomolangma, ____ appeared

a rare rainbow soon.

[ ]

A. of which

B. on which

C. from which

D. above which