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Present Perfect and Simple Past

In communities, read the brief grammar explanation about the difference between the present perfect and simple past tenses.

Present Perfect

Affirmative subject+ auxiliary venb have/has + venb in past panticiple + object or complement I have studied all the lessons for the exam.

Negative

subject + auxiliary venb have/has +not + verb in past participle + object or complement

She has not taken chemistry this period.

Interrogative

auxiliary venb have/has + subject + venb in past participle + object or complement + ?

Have you ever penformed an experiment at the new lab?

The present perfect is often used with time expressions which indicate time up to now,for example, today, this year, in the last six months.

Simple Past

Affirmative subject + verb in the past fonm+ object or complement I completed all my homewonk yestenday.

Negative

subject + auxiliary did+ not + venb in the base form+ object or complement

She did not take chemistry last semester:

Question

auxiliary verb did + subject + venb in the base form+ object or complement+?Did you perform an expeniment last period?

It is used with past time expressions such as yesterday, fwo weeks ago, last year.

Use the simple past when the action started in the past, finished in the past, and doesn't continue in the present. Use the present perfect when the action started in the past and continues in the present.

Grammar



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