说出已经结束的时间，比如 yesterday、last year 或 in 2019，就用一般过去时。
说出了已经结束的时间 → 一般过去时
I saw it yesterday.
We met in 2019.
试一试: Woman: Nice jacket! Is it new? Man: Yes, I ___ it last weekend. 选出那个男人会说的话。 (have bought / bought / lost) 答案: bought — Last weekend 是已经结束的时间，所以他说 bought。
没有已经结束的时间 → 现在完成时
没有已经结束的时间，就用 have / has + 过去分词：说到现在为止的经历，或者到现在还是这样的事。
I've been to Chicago.
I've lived here for two years.
试一试: Woman: Your car looks great! Man: Thanks. I ___ it for twelve years, and it still works well. 选出那个男人会说的话。 (had / have sold / have had) 答案: have had — 车现在还是他的，他已经有这辆车十二年了，所以是 has had。
just、already、yet：两种都可以
用 just、already 和 yet 的时候，美国人两种说法都用：I just ate 或 I've just eaten；Did you pay yet? 或 Have you paid yet?
I just ate. / I've just eaten.
Did you pay yet? / Have you paid yet?
试一试: Woman: Is your brother home? Man: Yes, he ___ home. He's in the kitchen. 选出那个男人会说的话。 (will get / just got / didn't get) 答案: just got — 他现在就在厨房里，所以 just got 合适（说 has just gotten 也可以）。
哪个更合适？
有已经结束的时间吗？用一般过去时。讲你到目前为止的人生，或者带着 for 或 since、到现在还是这样？用 have / has + 过去分词。
I opened my account in May.
I've had my account since May.
试一试: Man: Do you know Denver well? Woman: Yes. I ___ there for a month in 2020. 选出那位女士会说的话。 (stayed / have stayed / lost) 答案: stayed — In 2020 是已经结束的时间，所以她说 stayed。