Sheldon Cohen and His Colleagues Found That Development of Colds

Sheldon Cohen and his colleagues found that development of colds

A) was more strongly related to the duration of stress than its severity.
B) was not reliably related to the severity of the stress but was related to the presence of stress.
C) occurred only with both long-term stress and severe stress.
D) showed no relationship between previous stress and the subsequent development of colds.