Wegener's continental drift hypothesis was not widely accepted at first because _______.

• A. Because he couldn't offer an explanation of how the continents could have moved.
• B. Because continents are too heavy to move.
• C. Because there was no evidence at all.
• D. Because continents were fixed by gravity

Answer: (A)

The main idea being tested is why a bold hypothesis can struggle to gain acceptance without a plausible mechanism to drive the change it proposes. Wegener had strong observations—continents that seem to fit like puzzle pieces, matching fossils across oceans, and related rock and mountain belts—that pointed toward continents having moved. But he couldn't explain how such enormous landmasses could actually move through the oceanic crust. His proposed ideas about what could push or drag them (tidal forces, Earth's rotation, etc.) were not supported by the physics of the time, so the hypothesis lacked a credible driving mechanism. Because scientists look for a testable process, the lack of a convincing mechanism kept the idea from widespread acceptance despite the supporting evidence.

For example, the other explanations aren’t as accurate because they dismiss the evidence Wegener did have or attribute the problem to surface-level obstacles (like gravity or the continents being “too heavy”) rather than the missing mechanism. The important takeaway is that a convincing mechanism for movement is essential for a transformative theory to be widely embraced, which is why Wegener’s idea wasn’t accepted until later, when plate tectonics provided a workable mechanism.