Using Should | Could | Would have done correctly -- English Grammar lesson
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A lot of people get confused while using should/could/would with 'have + past participle verb'. In this lesson, you will understand the difference between three sentence structures and when to use them appropriately.
1. I should have completed my graduation : ('should' is used when a past duty/obligation not fulfilled. Also, when something was the correct thing to do in the past.)
You should have been more careful while travelling. (something that was the right thing to do in the past, but you didn't)
2. I could have completed my graduation : ('could' is used to express a past possibility, or an option you had in the past).
You could have helped me yesterday . (you had the option to help, but you chose not to)
3. I would have completed my graduation : ('would' is used to express that you do or don't do something due to circumstances and is used in past conditionals).
If I had gone to the beach, I would have gotten a tan. (it's an imaginary of something in the past).