a man in his thirties的用法和样例：
- A man in his 30s knocked on the door.
- We should not speak evil of a man in his absence.
- In that Club--more of a mausoleum, really--they'd look on a man in his forties as a mere slip of a boy.
- A man in his position might have done the same thing.
- He was a man in his late thirties, with fine, dark hair and a pale oval face.