I + Have + Past Participle of the verb.
For example: I have worked.
Both are correct depending on the situationdid not decide -- this is past simple negative and is used to talk about something in the past that is finished now.You did not decide what was right and you missed out.Have not decided -- this is present perfect negative and is used to talk about something that happened in the past that has a present result.You have not decided what is right and now you miss out.
not sure...anybody else???
amphetamine use and abuse in the U.S. from the 1950s to the present.
Green seals are used on all Federal Reserve Notes dated 1928 to the present.
Hudson
Present perfect, past perfect or future perfect.
"Cannot" can't be used in the present perfect tense.
Present perfect is formed with - have/has + past participle.The past participle proctor is proctored. So present perfect is have/has proctored.He has proctored us before.
"Has" is used with singular subjects in present perfect tense, "have" is used with plural subjects in present perfect tense, and "had" is used in past perfect tense. "Has" is used when the subject is singular in the present, "have" is used when the subject is plural in the present, and "had" is used when indicating an action that was completed in the past before another past action.
The present perfect tense is used when there is a connection with the past and the present. It is used to depict change, experience and a continuing situation. The future perfect tense, however, is used to talk about the past in the future.
Present perfect. Present perfect is formed with have / has + past participle. transformed is the past participle of transform
The present perfect tense can be used to express experience, a change or a continuing situation.
"Have" is present. "Had" is past tense
Have and has are both used in the present perfect tense:I/You/We/They have learned.He/She/It has learned.
present perfect tells us about the past and the present.
It is 'cost'. For example, if the noun used is first or third person plural, it is always 'have cost'; if the noun used is third person singular it is 'has cost'.Present perfect is have/has costThey/We/You/I have cost us a fortune.He/She/It has cost the school lot of money
Present Perfect Tense: I have; You have; he, she, it has; we have, you have, they have Past Perfect Tense: I had; you had; he, she, it had; we had; you had; they had Future Perfect Tense: I shall have; you will have; he, she, it will have; we shall have; you will have; they will have Note: has is used in the third person, singular present perfect tense.