a dutiful son的用法和样例：
- Being a dutiful son, Sun Quan had no choice but to marry his sister to Liu Bei. Zhou Yu's plan failed, but he thought up another one at once.
- Youyu Shi who was like a dutiful son came to the throne. His old father got ill because of his carelessness, so he hurried to come back to serve.
- Ronnie transformed from a lighthearted teenager into a devoted soldier and a dutiful son who called his mother every day from his post in Iraq.
- This teacher was a dutiful son.
- You've got a dutiful mother, you have, my son.
- A dutiful son is obliged to pay his father's debts