再请教

深海的小美人鱼

    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.
(E) Onset of the disease usually follows infection by both the virus and the bacterium.

答案D，B为什么不对

深海的小美人鱼

    Economies in which a high percentage of resources are invested in research and development show greater growth in the long run than do those in which resources are channeled into consumption. Japanese workers spend a higher percentage of their income investing in research and development than do American workers.
To grow as fast as Japan has in the past three decades, the United States must change the tax code in order to encourage savings and investment and discourage debt.
Which of the following, if true, tends to weaken the argument?
(A) Japanese research is more focused on consumers than is research by American firms.
(B) Class mobility, highly valued in American culture, is encouraged by a growing rather than a stagnant economy.
(C) Studies have shown that countries with high consumption rates prosper in the short run.
(D) Proposed changes to the tax code could involve strict limits on the deductability of interest, and increased allowance for research.
(E) Because a decreasing percentage of the United States is under 40, an age when savings are traditionally low, the savings rate will increase without changes to the tax code
答案E。不明白，请解释一下。谢谢

jediming

试解答如下：

  B support the idea
  --> bacterium causes disease(although virus AID bacterium)
or
  --> Both bacterium and virus cause disease

But C is critical evidence, because virus ALONE has been oberserved in many cases of the disease

D你为什么认为support呢？