a Bill oBligatory的用法和样例：
- The store sent me a bill for $50.
- This is a bill payable on demand.
- He paid for the goods sent him from Detroit by a bill of exchange.
- I'm the bearer of a bill of exchange drawn on you.
- Offence of remove goods without pay for them or of refuse to pay a bill.
- A bill of fare is very helpful to TV viewers.