Present perfect or simple past with "for the last twenty minutes"?

Question

My teacher  give me a question

You know she (stand)______ looking at that picture for the last twenty minutes.

and my job is complete this sentence with any verb tense provided it makes sense.

My teacher said it must be present perfect:

You know she has stood looking at that picture for the last twenty minutes.

But I think the simple past is correct:

You know she stood looking at that picture for the last twenty minutes.

It seems to me "for the last twenty minutes" is a completed time period, it can't include the present moment. So we can't use the present perfect.

Can you explain to me which is correct?

hbtpoprock · Answer

If I were you, I would use present perfect continuous.

You know she has been standing (and) looking at that picture for the last twenty minutes (until now and so on).

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