half an hour的用法和样例：
- The vicar preached to the congregation for half an hour.
- The assignment is few enough to be finished within half an hour.
- The whole job only takes half an hour.
- Would you give me half an hour to converse with you?
- It took him half an hour to finish the work.
- The train to Beijing will depart from platform 3 in half an hour.
- The two fighters battled for half an hour.