12. A newly discovered disease is thought to be caused by a certain bacterium. However, recently released data notes that the bacterium thrives in the presence of a certain virus, implying that it is actually the virus that causes the new disease.
Which of the following pieces of evidence would most support the data’s implication?
(A) In the absence of the virus, the disease has been observed to follow infection by the bacterium.
(B) The virus has been shown to aid the growth of bacterium, a process which often leads to the onset of the disease.
(C) The virus alone has been observed in many cases of the disease.
(D) In cases where the disease does not develop, infection by the bacterium is usually preceded by infection by the virus.（C）
(E) Onset of the disease usually follows infection by both the virus and the bacterium.
why not B? | 
