a family of four的用法和样例：
- A family of four perished in the fire.
- There was a family of four visiting a cruise ship.
- He couldn't earn enough to keep a family of four.
- I simply could not conceive of a family of four living in such a small room?
- They are a family of four and want to stay together.
- A trip to a Lakers game will cost a family of four a whopping $453.95.