What combination did Duane tell Nick to retrieve his biology book?

The combination 5-3-5 signifies a specific sequence that Duane communicated to Nick for retrieving his biology book. In contexts like lock combinations or numbered systems, each number often corresponds to a precise position or location.

Using "5-3-5" suggests that Nick needs to access the fifth object or location first, then proceed to the third, and finally return to the fifth again. This sequence highlights a methodical approach that might be needed to locate the book effectively. It is likely that the first and third numbers being the same indicates a point of retrieval or confirmation of the chosen item after navigating through another position.

The other combinations, while consisting of numbers, do not align with the contextual cues and instructions provided by Duane, making them unsuitable for the task at hand.