The correct answer is A.
Fungi can reproduce asexually while animals cannot.
Performance can be impaired by a fluid-related decrease in body weight of as little as 1 percent. Dehydration is assumed to be a major adverse effect associated with rapid loss of body mass and this impairs the level of performance in an individual.
This might have been the cause of not being exposed to this specific pollen during his years in Chicago. Allergic reactions can develop when the stimuli presented even when its not contagious causes the immune system to trigger and act in a defensive stance. This delayed effect may have been the cause of the sudden expression of the immune system.