Thousands of athletes______ in many countries will compete _______ medals in the 2008 Olympic Games in Beijing.

A．involved; in

B．involving; by

C．to involve; against

D．involved; for

下列关于应收账款周转率的说法中，正确的有______。

A．应收账款周转率说明应收账款流动的速度

B．应收账款周转率越高，平均收账期越短，应收账款的收回越快

C．应收账款周转率是企业从取得应收账款的权利到收回款项，转换为现金所需要的时间

D．应收账款周转率等于销售收入与期末应收账款的比值