Which One of the Following Groups of Factors Includes Something

Which one of the following groups of factors includes something not known to cause physiological dysfunction?

A) abnormal immune response, excessive cold, infection by a pathogenic bacterium, reduced oxygen supply
B) abnormal immune response, excessive cold, infection by a pathogenic bacterium, vitamin B₁₂ deficiency
C) abnormal immune response, excessive cold, infection by a pathogenic bacterium, alcohol excess
D) abnormal immune response, excessive cold, infection by a pathogenic bacterium, vitamin D supplementation in older people