'I have eaten' is the present perfect tense of the verb 'to eat', 'I had eaten' is the past perfect and 'I will have eaten' is the future perfect.
Ihave eaten是动词eat的现在完成时；Ihad eaten是过去完成时；Iwill have eaten是将来完成时。
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。
We use the present perfect tense to talk about things that started in the past and still have some connection with the present.
我们用现在完成时来谈论在过去开始并且仍与现在有联系的事情。
We use the present perfect tense to talk about something that happened at an indefinite time in the past.
我们使用现在完成时谈论发生在过去某个不确定的时间的事情。
Rewrite the following sentences using the present perfect passive voice.
用现在完成时的被动语态改写下列句子。
Change these sentences into the present perfect passive putting the verbs into the correct forms.
用动词的正确形式将下面的句子变成现在完成时的被动语态。
When we talk about past events which have no present importance, we do not use the present perfect.
谈论过去的事件其对现在不重要，不用现在完成时。
For example, try to write down each example of a form you are studying such as the present perfect.
比如，列出你正在学的语法知识的全部形式，如现在完成时。
The question is in the present perfect continuous so you will answer with the verb in the continuous.
For example：这个问题是用现在完成进行时来提问的，所以回答时也用进行时态的这个动词。
The present perfect is used to express an action that started in the past but still continues in the present.
现在完成时用来表达开始于过去但仍在现在持续的动作。
We often use the present perfect to give news: it is especially common in reports, letters and conversations.
我们经常用现在完成时态来说新闻：尤其常见于报道、信函、会话。
In this case, the past or present perfect tense should be used according to the grammatical rules of common English.
若按普通英语的动词时态规则，就得用一般过去时或现在完成时。
In English learning, it is difficult for learners to master the tense, especially the past tense and the present perfect tense.
英语学习中，时态的学习和运用对学习者尤其中低水平学习者来说是一个困难之处。
The second function of the present perfect continuous tense is to talk about an action that started in the past and it is still happening.
第二种：谈论一个起始于过去，但是现在仍在发生的动作。
At first glance it looks as if there is no element of "present involvement" in this use of the present perfect any more than in the simple past.
乍看起来，在现在完成时的用法中，似乎跟在一般过去时中一样，都没有“涉及现在”的因素。
They appear more excited when we talk about university life in the United States than when we discuss the correct usage of the present perfect tense.
与讨论如何正确使用现在完成时相比，当我们谈起美国大学的生活时，他们显得更为兴奋。
As one of the most important and confusing grammatical tenses in high-school English, present perfect tense brings about much perplexity to both teachers and students.
现在完成时态是中学英语语法中的重点和难点，经常给师生带来困惑。
We use the present perfect continuous (I have been doing) for situations over a short time. We use the present perfect (I have done) for situations that exist for a longer time.
现在完成进行时用在短时间的情况，现在完成时用于长时间的情况。
So you learn the past tense and then two or three weeks later, oh now you are learning the present perfect, and then a few weeks later, you are learning the future, that's crazy.
你学习了过去时，然后两到三周后你开始学习现在完成时，几周以后你又开始学习将来时，这简直太疯狂了。
When we want to talk about actions or situations which started in the past and have continued up to the present, we often use the present perfect to show the connection between past and present.
要谈论行为或状态其始于过去而持续到现在，经常使用现在完成时表现过去和现在之间的连接。
By combining theories and experiment, this thesis compares and analyzes the features in the process of learning English present perfect by both Chinese Han students and Chinese ethnic Korean students.
本文通过理论和实验相结合的方法，对比分析单、双语人学习英语现在完成体的特征。
Change these sentences into the Present Perfect Passive, putting the verbs into the correct forms.
用动词的正确形式将下面的句子变成现在完成时的被动语态。
I want to be a practical teacher, so when I am working, I prefer to use'the Present Continuous Tense'or'the Present Perfect Tense'instead of'the Future Tense.
我给自己的定位是做一个笃行务实的老师，与其在工作中一直说“将来时”，我个人更倾向于使用“现在进行时”或者“现在完成时”。
I want to be a practical teacher, so when I am working, I prefer to use'the Present Continuous Tense'or'the Present Perfect Tense'instead of'the Future Tense.
我给自己的定位是做一个笃行务实的老师，与其在工作中一直说“将来时”，我个人更倾向于使用“现在进行时”或者“现在完成时”。
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