a head of celery的用法和样例：
- He dug up a head of celery and gave it to the cook.
- I'll take a pineapple, a head of cauliflower, two bunches of celery, and a head of lettuce.
- The President cannot rudely ignore a head of state.
- He that have a head of wax must not walk in the sun.
- two bunches of celery, and a head of lettuce.