Passage Summary: There are iguanas on some islands near Australia that are only found there and in the Americas. Since the islands didn't exist when the continents were connected, the scientist thinks they must have floated across the ocean on logs or trash.

Conclusion: The ancestors of the iguanas on the Australian islands must have traveled there by rafting on debris from the Americas across the Pacific.

Reasoning: These iguanas and their American relatives are the only ones of their kind, and the islands appeared after the supercontinent Gondwana had already broken apart.

Analysis: The scientist assumes that because the islands formed after the split, rafting is the only way they could have arrived. To weaken this, we need an alternative explanation for how they got there or evidence that rafting was impossible. Look for an answer that suggests the iguanas could have come from somewhere else or that the landmasses were connected in a way the scientist didn't consider.