a quarter of a的用法和样例：
- A quarter of a pound of tea. And a tin of tobacco.
- I lost my head in a quarter of a minute.
- He led by three lengths after a quarter of a mile.
- A quarter of a pound of ham, please.
- The house failed to reach its agreed price, and was bid in at a quarter of a million pounds.
- The force numbered almost a quarter of a million men.