a pair of stockings的用法和样例：
- She has lost a pair of stockings.
- A pair of stockings paired with a short skirt is popular this year.
- I bought a pair of tan leather shoes the other day.
- Mary's going to buy a new pair of stockings, is not she?
- She wears a pair of sheer stockings.
- Mrs. Brown wants to buy a pair of stockings and she asks the assistant about them.