If the Metropolitan Museum of Art had not decided to display together

more simple (and among all the answer choices) that make up its Picasso collection is the only tense that make sense for the overall structure of the sentence.

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.

this good question make us choose between A and B, or between simple present and present perfect

I review grammar book a little bit. this point is very basic and person who learn english well can do this question easily

simple present show an condition which is thought to exist indefinitely. in constrast, present perfect which show an action which is finished at the point in past but its time frame prolong from past to present, or an action began in the past and prolong to present.
in the case present perfect show a finished action, its time frame is unfinished and it go with unfinised time word such as this month, this year.... this case show that finished action presented by present perfect is relevant to present. I have learn english this week. this mean that this week I have to learn english and I have done my job for this week. the time frame is from the past to present. honestly, i see that meaning in this case of present perfect is hard. mechanically we can remember that a finished action go with unfinished time word or with no time words is used with present perfect.

differentiating present simple and present perfect is the key to understanding simple past and past perfect, the key to understanding all basic tenses in gmat.

Bunuel
there is not comma before that in B. so doesn't that mean "that " is modifying just the sundry items. but in C since there is comma before that it modifies the whole list. As the whole list was part of the collection

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