请教：大全C－12

Which of the following best completes the passage below?

Monarch butterflies, whose average life span is nine months, migrate from the midwestern United States to selected forests outside Mexico City. It takes at least three generations of monarchs to make the journey, so the great-great-grandchildren who finally arrive in the Mexican forests have never been there before. Yet they return to the same trees their forebears left. Scientists theorize that monarchs, like homing pigeons, map their routes according to the earth’s electromagnetic fields. As a first step in testing this theory, lepidopterists plan to install a low-voltage transmitter inside one grove of “butterfly trees” in the Mexican forests. If the butterflies are either especially attracted to the grove with the transmitter or especially repelled by it, lepidopterists will have evidence that______

(A) monarch butterflies have brains, however minuscule

(B) monarch butterflies are sensitive to electricity

(C) low-voltage electricity can affect butterflies, whether positively or adversely

(D) monarchs map their routes according to the earth’s electromagnetic fields

(E) monarchs communicate in intergenerationally via electromagnetic fields

（B）文中并没有出现electricity啊，为什么选B？我觉得C更正确啊。。请教。。。

I support B. If low-volt transmitter effects the behavior of monarch butterflies, then we can conclude that they are sensitive to electricity.

A is irrelevant. D and E are taking one step too far. C has two problems 1) the subject should be limited to Monarch Butterflies, not all butterflies 2) we have no context to define the positive and adverse effect.   

哦。。。明白了，我之前是在B和C之间徘徊，觉得 low-volt transmitter 和electricity没有必然联系，而 either especially attracted to the grove with the transmitter or especially repelled by it则表示了positively or adversely，所以觉得C正确，但忽略了C中没有针对monarch butterflies，这点比较致命。。。

谢谢jandjshi的详细解释啦。。。