导游人员的聚谈艺术——认真倾听体现在( )。

A．约束自己，集中思想

B．主动反馈，心领神会

C．尊重对方，平等交谈

D．适当沉默

The experiment has（）the possibility of the existence of any life on that planet, but it does not mean there is no life on other planets.

A. found out

B. pointed out

C. ruled out

D. carried out