a serious young man的用法和样例：
- He was a serious young man, not rakish or loud-voiced like the others.
- They watched in awe as Revere, at first a callow and unambitious youth, began to develop into a serious young man dedicated to books and devoted to his father.
- He is a serious young man.
- He was a serious young man, not rakish or loud-voiced like the others
- He was a very serious child and grew up to be a very serious young man.