单选题 From the last two paragraphs we can conclude that ______.

A、 exchange students are welcome in America
B、 exchange students must pay much money to the host families
C、 American students don't want to join the exchange programs
D、 old Americans can benefit from hosting exchange students

【正确答案】 D

【答案解析】推理题。根据本文最后一段“For elderly people，exchange students”keep us young-they really，“said Jean Foster，who is hosting 16-year-old Nina Porst from Denmark．”一个接收了一名16岁丹麦少年的老人的话中我们可以知道，这些孩子带给了老人们活力，让他们青春常驻。所以，[D]正确。