Final answer:
Without specific context, it is impossible to accurately determine if Moss arrived on the island 'By boat' or 'By plane.' The correct answer would depend on the definition of aircraft or ship used in the context of the question.
Step-by-step explanation:
The question seems to be regarding the mode of transportation used by a character named Moss to arrive on an island. Given the provided reference information that the only ways to get to the islands are by aircraft or by ship, it suggests that Moss could have arrived either by boat (Option A) or by plane (Option D). The other provided options, by helicopter (Option B) and by swimming (Option C), would generally not be included under standard definitions of aircraft or ship, unless 'by helicopter' is considered a subtype of 'by aircraft.' Therefore, if 'helicopter' is not broadly classified as an 'aircraft' for the purposes of this question, the correct answer would likely be 'By boat' or 'By plane.' However, without specific context from a text or a story, selecting the precise method of Moss's arrival is impossible. If the question is from a literary work or text, students should refer back to the material to find the correct answer.