Correct Response: B. The primary reason so many scientists rejected Alfred Wegener's idea of continental drift was that his idea lacked a mechanism that could cause continents to move. Without a convincing mechanism to support his hypothesis the geologic community was not ready to accept such a radical idea. Some scientists did consider Wegener an outsider in the field of geology, but because he was a respected scientist with strong evidence, he was never considered an amateur (A). Wegener frequently and enthusiastically defended his theory of continental drift (C), publishing a book on the topic and giving lectures. Though Wegener struggled to come up with a mechanism, he was an accomplished scientist and the evidence he collected was widely accepted even if his theory explaining it was not (D).