According to the excerpt, the option that identifies an implicit meaning one could draw from it would be the second one: "Locke is unfamiliar with the term idea".
In the excerpt, Locke is not asking what Idea is nor is he being uncertain about the relationship between speculative and practical ideas. He seems to never heard it before and the exact meaning fades away.
That's why he asks what it represents and not its definition or for someone to repeat the explanation. He just needs an example to clarify the boundaries of the idea's meaning.
