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 very serious child and grew up to be a very serious young man.
- a serious student of history; a serious attempt to learn to ski; gave me a serious look; a serious young man; are you serious or joking?; Don't be so serious!