have or has

[Trouper]

Dear English experts,

Check my answer my below

Where was sally yesterday? she might have or has been seeing doctor.

Please explain your answer

Thanks

[Jamie (K)]

Before I can give an answer and explain it, I need to know what your question is.

The first problem I see right away is that you don't use any capital letters.

[Trouper]

My question is very simple: Why we say he might have been but not he might has been?

thanks

[Alan]

Hi,

Let's start from the beginning. The modal verbs like can/could, may/might/will/would are followed by either simple or perfect infinitive forms. We say: He may go today where 'go' is the simple infinitive but if we want the past form, we say: He might have gone yesterday where 'have gone' is the perfect infinitive. That's why you say: 'he might have been.'

Alan
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English as a Second Language
You can read my ESL story Phrasal Verbs/hold