Question

10. She is proud of her two sons,        is now studying in the US. (young)

她为他的两个儿子感到骄傲，其中年纪较小的那个正在美国读书。

Answer 1

10. the younger of whom考查非限制性定语从句。形容词比较级前加定冠词，表两者间特指的那一个。