117. A certain viral infection is widespread among children, and about 30 percent of children infected with the virus develop middle ear infections. Antibiotics, although effective in treating bacterial infections, have no effect on the virus. Yet when middle ear infections in children infected with the virus are treated with antibiotics, the ear often clear up.

Which one of the following most helps to explain the success of the treatments with antibiotics?

(A) Although some types of antibiotics fail to clear up certain infections, other types of antibiotics might provide effective treatment for those infections.

(B) Children infected with the virus are particularly susceptible to bacterial that infect the middle age.

(C) Many children who develop middle ear infections are not infected with the virus.

(D) Most viral infections are more difficult to treat than are most bacterial infections.

(E) Among children not infected with the virus, fewer than 30 percent develop middle ear infections.

在原文没明确指出中耳炎是由bacterial引起的情况下，可以如此肯定的推出答案B吗？

原文是没有说，但问题问得是"...most helps to explain..."。这就是让我们加一个条件，使题目的结论成立。

原文说antibiotics对bacterial infection有效，而结论说antibiotics对middle ear有效。它们之间需要一个条件作为桥梁把它们连接起来。答案B立刻就stand out了。

1，原题中，antibiotics对bacterial infections有效，对the virus无效.

2，得了中耳炎，同时感染了the virus,用antibiostics治疗，耳朵常常复原。

3，根据1，2，可以建立一种联系，bacterial可能是中耳炎的诱因之一。

期待nn们的解释~~~~~~