a classified ad的用法和样例：
- A classified ad is usually only a few lines long.
- I placed a classified ad for a secretary last Monday.
- However, running a classified ad in the newspaper is still one of the most popular ways to recruit full-time staff.
- Roy:So, what, placing a classified ad didn't have the right undertone of personal violation for you?
- This would be a perfect time to kick off an advertising or publicity campaign for your business, or to run a classified ad, but not to find romance - do that in early May.