at 表地点时，指空间位置上的某一点；表时间时，指在时间上的某一时刻。
in 表地点时，指在某一立体空间范围内；表时间时，指一段时间或与年、月、季节时间连用。
on 表地点时，指某物与另一物表面相接触，或与某地方接壤等；表时间时，指在某一天或某一天的某个时间，尤指在星期几。
参考例句
1. You made a mistake in leaving her alone. 你将她一个人留下是错误的。
2. We all live in the past. We take a minute to know someone, one hour to like someone. 我们每个人都生活在各自的过去中，人们会用一分钟的时间去认识一个人。
3. Please put your laundry in the paper bag and write down the contents of the laundry on it. 请将你需要洗的衣服放在纸袋中，不再理会这些琐事，并将衣物内容写下来。
英英解释
n.
1. a unit of length equal to one twelfth of a foot
2. a rare soft silvery metallic element; occurs in small quantities in sphalerite
3. a state in midwestern United States adj.
1. holding office
2. directed or bound inward
3. currently fashionable adv.
1. to or toward the inside of
