如何使用 "an" 造句

1. But that was not an option .
但这不是一个选择。
2. They wanted an outdoor life .
想要一种野外生活。
3. Get specific about the behavior and offer an alternative to it .
务必将信息反馈具体到某一具体行为并提供可选方案。
4. On the steep bank of an actual river .
但并不是对每一种死法都赞同。
5. This seems to be an impasse .
这似乎是一个僵局。