1. He has been an active participant in the discussion. 他一直积极参与这次讨论。
2. As an active participant in various volunteer work, I have a lot of experience in serving others. 作为一个积极参与各种志愿活动的人，我在服务他人方面有很多经验。
3. In the past few years, Math Counts added two new middle school programs to try to diversify its participant pool. 在过去的几年里，Math Counts 增加了两个新的中学项目，试图使其参与者多样化。
4. For one trial, each participant was shown a pile of pens that the researcher claimed were from a previous experiment. 其中一项试验中，研究人员向每一位参与者展示了一堆笔，并声称这些笔来自先前的一项实验。
5. He described one study participant, still working at the age of 100, who was recently disappointed to see his son retire. 他描述了一位100岁仍在工作的研究参与者，这名参与者最近因看到自己的儿子退休而感到失望。
