If the Metropolitan Museum of Art had not decided to display together the 34 paintings, 58 works on paper, two sculptures and sundry items including prints that have made up its Picasso collection, some truths and questions about the most important figure of 20th century Western art might not have been aired.

If the Metropolitan Museum of Art had not decided to display together the 34 paintings, 58 works on paper, two sculptures and sundry items including prints that have made up its Picasso collection

If the Metropolitan Museum of Art had not decided to display together the 34 paintings, 58 works on paper, two sculptures and sundry items including prints that make up its Picasso collection

If the Metropolitan Museum of Art would not have decided to display together the 34 paintings, 58 works on paper, two sculptures and sundry items including prints, that make up its Picasso collection

If the Metropolitan Museum of Art would not have decided to display together the 34 paintings, 58 works on paper, two sculptures and sundry items including prints that have made up its Picasso collection

If the Metropolitan Museum of Art had decided to display together the 34 paintings, 58 works on paper, two sculptures and sundry items including prints, making up its Picasso collection

OA
Can we have discussion on A vs B?
How the present perfect distorts the sentence?
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Prepositional Phrases Clarified|Elimination of BEING| Absolute Phrases Clarified
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Agree with PraPon


A- 'have made up' indicate that A,B,C,and D including E.... were part of the collection ONLY till that point (when museum displayed all of them together)

while B says--'that make up' -indicating that these items are still a part of the collection. We have No reason or information that tells us otherwise. So B>A
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Can we have discussion on A vs B?
How the present perfect distorts the sentence?

If the Metropolitan Museum of Art had not decided to display together the 34 paintings, 58 works on paper, two sculptures and sundry items including prints that have made up its Picasso collection, some truths and questions about the most important figure of 20th century Western art might not have been aired.

A) If the Metropolitan Museum of Art had not decided to display together the 34 paintings, 58 works on paper, two sculptures and sundry items including prints that have made up its Picasso collection

B) If the Metropolitan Museum of Art had not decided to display together the 34 paintings, 58 works on paper, two sculptures and sundry items including prints that make up its Picasso collection

C) If the Metropolitan Museum of Art would not have decided to display together the 34 paintings, 58 works on paper, two sculptures and sundry items including prints, that make up its Picasso collection

D)If the Metropolitan Museum of Art would not have decided to display together the 34 paintings, 58 works on paper, two sculptures and sundry items including prints that have made up its Picasso collection

E) If the Metropolitan Museum of Art had decided to display together the 34 paintings, 58 works on paper, two sculptures and sundry items including prints, making up its Picasso collection


Here,
I was also confused between would not have decided and had not decided. (It will help if anyone can clarify this.) So, I sought for other errors. Sentence has If X, Y construction.
I would shorten the sentence by skipping the modifiers for a moment as below.
If the Museum had not decided X, Y and Z, some truths and questions might not have been aired. Correct.

To discuss between A and B, The confusion lies between simple present sentence Or simple perfect tense.
A uses prints that have made up its Picasso collection.
B uses prints that make up its Picasso collection

It is the fact that is true not only in past but also in present. Present perfect used for actions completed in the past. So, Usage of simple present tense is correct one.