英语流利说 Level 6 Unit 1-2 Talking a
When we talk about experience or results, we use the present perfect form.
This form uses "have" followed by the participle.
For regular verbs, this participle is identical to the past tense form.
For irregular verbs, this participle is often different.
When we use the perfect form, the primary focus is on the subject of the sentences, not the verb.
It emphasizes condition, experience or results rather than actions or events.
In these two examples, we see the contrast.
英语流利说 Level 6 Unit 1-2 Talking about Verbs 2
The top sentence gives the condition or state of the subject and the bottom sentence expresses an event.
The top sentence describes the condition of the subject of the sentence, she, rather than an event.
The fact that she has left the hotel is now a part of her experience, or state of being.
The bottom sentence expresses the action, or event: "she left," which is something she did.
In general, the past tense form expresses events or acts, and the perfect form expresses experience or conditions.
When we use the perfect form of the verb we focus on the state of the subject and not an action or event.
（He enjoyed his studies and graduated a few months ago. Now that he has graduated，he's ready to get a job.）
Note that the past form expresses events at specific points or periods of time, such as last year or the past five years.
These events are distanced from the speaker's point of view.
The perfect form expresses the state of something from the speaker's point of view, not distanced in time.
These two sentences are incorrect and confusing, because they give two different points of view.
英语流利说 Level 6 Unit 1-2 Talking about Verbs 2
Here are some sentences that use the perfect form.
Some are simple, such as the first one, and some are complex, like the last one.
英语流利说 Level 6 Unit 1-2 Talking about Verbs 2
The last one is complex because it combines many verb forms, including the passive.
（He may have been injured in the explosion.）
（The game has started already.）
（He may have taken his computer with him，but I'm not sure if he did or not.）
（It has been getting warmer lately.）
（He may have been arrested by the police.）
（His computer may have been taken by somebody.）
