I know this has been posted a number of times, but I really need a clear answer to this one

When storing Renaissance oil paintings, museums conform to standards that call for careful
control of the surrounding temperature and humidity, with variations confined within narrow
margins. Maintaining this environment is very costly, and recent research shows that even old
oil paint is unaffected by wide fluctuations in temperature and humidity. Therefore, museums
could relax their standards and save money without endangering their Renaissance oil
paintings.
Which of the following is an assumption on which the argument depends?
A. Renaissance paintings were created in conditions involving far greater fluctuations in
temperature and humidity than those permitted by current standards.
B. Under the current standards that museums use when storing Renaissance oil paintings,
those paintings do not deteriorate at all.
C. Museum collections typically do not contain items that are more likely to be vulnerable
to fluctuations in temperature and humidity than Renaissance oil paintings.
D. None of the materials in Renaissance oil paintings other than the paint are vulnerable enough to relatively wide fluctuations in temperature and humidity to cause damage to
the paintings.
E. Most Renaissance oil paintings are stored in museums located in regions near the regions
where the paintings were created.


What I don't understand is that the argument clearly states that "old
oil paint" i.e paint from Renaissance paintings were unaffected by temperature fluctuation, so the assumption made here is old paint is sturdy enough to withstand the fluctuating temperature correct, then how come we have accepted 'D' as the right answer when it categorically states that 'None other than the paint ' are vulnerable to wide fluctuations in temperature.

Please provide a detailed explaination. Thanks
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GMAT the final frontie!!!.

Fact: Current standard has narrow range of temperature/humidity
Fact: Old paint is unaffected by wider range of temperature/humidity
Conclusion: museum can relax its restrictions.

It might be good if Renaissance paint doesn't deteriorate "at all" using the current standards. However, let's say that the Renaissance paint deteriorate slightly, does this negate the conclusion? No, not really. To reach the conclusion, all you need is that Renaissance paint deteriorate the same amount as before. Therefore, the assumption that Renaissance paint doesn't deteriorate "at all" is extreme. The words "at all" makes B incorrect.

D is better because if other materials deteriorate under wider range of temp/humidity, then the painting will surely deteriorate.