Which of the following, if true, most seriously weakens the force of the evidence cited above? A. Being chilled is a form of stress, and stress lowers the defenses of a person's immune system, which guards against infection. B. After a rhinovirus has incubated in a person for several days, the first symptom it causes is a feeling of chilliness. C. People who are tired and then become chilled are more likely to catch severe colds than are people who are chilled without being tired. D. Some people who catch colds are not sure what it was that allowed them to catch cold. E. Rhinoviruses are not always present in the environment, and so a person could become chilled without catching a cold.