an的例句：
I think you have made an error in calculating the total.
我想你在计算总数时出了差错。
We put an ad in the local paper.
我们在当地报纸上登了一则广告。
The government's policy is an open door to disaster.
政府的政策为灾难敞开了大门。
This door should only be used in an emergency.
这道门只能在紧急情况下使用。
He's an expert at getting his own way.
他在如何达到自己的目的方面很在行。