present perfect

基本解释

When you ask about something that started in the past but continues to the present time, you use the Present Perfect tense, e.g.
当你谈论从过去开始一直持续到现在的某件事时，用现在完成法时态。
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When you ask about something that started in the past but continues to the present time, you use the Present Perfect tense, e.g.: I’ve been there for 5 years / I’ve been there for 5 years.
当你谈论在过去开始但是一直持续到现在的某事时，用现在完成时态，例如：I’ve been there for 5 years/我在那里已经5年了。
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If we say when a past event happened (for example, by using time-adverbs), we do not usually use the present perfect.
说过去发生的事件（例如：用过去时间状语），我们通常不用现在完成时。
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In grammar, the present perfect tenses of a verb are the ones used to talk about things that happened before the time you are speaking or writing but are relevant to the present situation, or things that began in the past and are still happening. The simple present perfect tense uses "have" or "has" and the past participle of the verb, as in "They have decided what to do."