GMAT Critical Reasoning (CR) | Re: When storing Renaissance oil paintings, museums conform to

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