Hello , I need help . I'm not an English native speaker and I don't understand some measures
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What's the difference in meaning between the use of different tenses in the following sentences :
1.
a.) Come over and see us when our guests leave .
b.) Come over and see us when our guest hav left .
2.
a.) He says he has seen a meteor at some time .
b.) He says he saw the meteor last night .
3.
a.) I was a colleague of hers , working in the same Department , for several years .
b.) I have been a colleague of hers , working in the same Department , for several years .
4.
a.) How far did you get ?
b.) How far have you got ?
5.
a.) She made a fool of herself in public .
b.) She has made a fool of herself in public .
6.
a.) Did anyone go ahead with the project ?
b.) Has anyone gone ahead with the project ?
7.
a.) Did you see the exhibition ?
b.) Have you seen the exhibition ?
Thank you in advance .