Which of the following statements about darkrooms is TRUE?

The statement regarding the need for processing tanks to be stainless steel to prevent corrosion is accurate. Stainless steel is a preferred material in darkrooms for processing photographic films because it has excellent resistance to corrosion and chemical damage. Given that processing tanks are frequently exposed to various chemicals used in film developing and fixing, the use of stainless steel helps ensure durability and longevity of the equipment. Moreover, this material is easy to clean and maintains hygienic conditions crucial for film processing, thereby contributing to consistent quality in image production.

The other statements do not hold true. Leaving open bottles in the processing room can lead to contamination and improper exposure of film, as it introduces additional variables that could affect density and processing results. Painting walls black is not necessary to absorb light from the safelight; by using safe lighting methods, film processing can be performed without the risk of exposing unprocessed film. Therefore, the only accurate assertion among the options is that processing tanks should ideally be made of stainless steel to prevent corrosion.