(D) Snakes are also absent from other major islands, such as Hawaii, Ireland, and Greenland.
This statement, if true, would strengthen the conclusion of the argument by showing a pattern that snakes are absent from other major islands, not just New Zealand. This supports the idea that snakes were unable to make the journey to these islands due to their inability to swim.
Explanation for other options:
(A) The presence of snakes in South America at latitudes farther south than New Zealand does not provide a reason for their absence in New Zealand or explain the connection between swimming and their distribution.
(B) While this statement highlights the efforts of island nations to prevent the accidental introduction of snakes, it does not strengthen the argument that snakes are absent from New Zealand due to their inability to swim.
(C) Sea snakes can swim, but this statement does not address the absence of snakes in New Zealand, nor does it provide evidence supporting the conclusion that other types of snakes could not make the journey.
(E) The presence of snakes on other Pacific islands does not explain why snakes are absent from New Zealand or strengthen the argument that their inability to swim is the reason for their absence.
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