The correct answer is A: It did not explain the mechanism causing the movement of continents.
At the time Alfred Wegener proposed the theory of continental drift, one of the primary criticisms was that he could not provide a convincing explanation for how the continents were able to move. Although he presented compelling evidence, such as the fit of the continents and similarities in fossil records, the lack of a defined mechanism to explain the drift led to skepticism and rejection of the theory by many scientists.