a bridge of four spans的用法和样例：
- It's a bridge of steel framework.
- A shared anguish can be a bridge of reconciliation.
- Life is a bridge of sighs across the flood of tears.
- We both realized that a bridge of understanding that spans almost 12000 miles and 22 years of hostility can't be built in one week of discussions.
- Our cat has a litter of four kittens.