单选题 The author mentions that the maximum THR for older adult participants in sports should he less than ______ beats per minute.

【正确答案】 B
【答案解析】[试题分析] 浏览查询细节题。
[详细解答] 文章中的第四段谈到“...the THR should not exceed 120 beats per minute.”据此可知B是正确答案。