Food may have no residues at all because of which of the following reasons?

The presence of no residues on food can indeed be attributed to the degradation of those residues over time. Pesticide residues may break down through various processes, including chemical reactions, microbial action, or even exposure to sunlight. This natural degradation can render the residues undetectable by the time the food reaches the consumer, which is why some foods might show no detectable levels of applied chemicals.

The other choices highlight scenarios that are also related to residue presence but do not specifically explain the degradation process. For instance, food may have no residues if it has not been treated with pesticides at all or if it has been washed thoroughly; however, these scenarios do not involve the breakdown of existing residues. Improper storage might lead to other issues such as spoilage but does not directly influence the levels of pesticide residues. Thus, the correct answer focuses on the biochemical processes that eliminate residues from food.