a friend of ours的用法和样例：
- A friend of ours closed escrow on his new home on a Sunday.
- Ash: We can't bury Shelly - S-She's a friend of ours.
- I would like you to meet a friend of mine.
- On our way to Shanghai we turned aside to Jinan to see a friend of mine.
- They were off to visit a friend of theirs.
- He was married to a friend of mine.