Use of Have/Has

Can is not used with the modals, but your other are.

We use them before have.

"I could have been an engineer if i had worked harder in university."

"James might have gone to the party. I'm not sure because I wasn't there."

"It may have rained last night. Check if the road is wet."

As you can see we use this form to specultate about past events. i.e. things we thinnk could have happened in the past.

Take a lool at these two pages on our site for more information:

Third Conditional

Speculating about Past Events

I have done as y mentioned link, there was two mistake in first while one is second one.

Could you please tell me how can i write better word while writing.

Thanks for y support.

Has is used with singular noun. Have is used with plural noun.
may:
We can use 'may' to ask for permission. However this is rather formal and not used very often in modern spoken English
May I borrow your pen?
We use 'may' to suggest something is possible

It may rain later today.
I may not have time to do it today.

might:
We use 'might' to suggest a small possibility of something. Often we read that 'might' suggests a smaller possibility that 'may', there is in fact little difference and 'might is more usual than 'may' in spoken English.
For the past, we use 'might have'.

He might have tried to call while I was out.
I might have dropped it in the street.

She might be at home by now but it's not sure at all.
It might rain this afternoon.

may is uncertain in a sentence.can advocate your ability

Could u pls share ur viewpoints on how to use 'over' in sentences...
Thanks

As you can see we use this form to specultate about past events. i.e. things we thinnk could have happened in the past.