Potential plot points: Protagonist hears rumors about exclusive papers, seeks out the library or a secret location, encounters challenges (like puzzles based on biology concepts), faces moral dilemmas if the papers are meant to be hidden, and resolves the story by using the papers to prepare but learns something deeper.

I need to make sure the story is engaging and highlights the importance of the past papers in a unique way. Maybe the exclusive papers are not just practice questions but have some unique features, like historical significance or rare questions that have never been published before.

The final challenge leads Li Wen to Labrador Nature Reserve. Mr. Tan himself—now 92 and wheelchair-bound—greets her. Grinning, he poses a final question:

Possible title: Maybe something like "The Guardian of Knowledge" or "Exclusive Papers of the Junior Olympiad." Alternatively, a title that includes Singapore and the Olympiad.

“How do mangroves, which thrive in saltwater, produce fresh fruit?” (Answer: By excreting salt through their leaves and using selective osmosis. )

First, I should set the scene in Singapore. Maybe a school or a competition setting. The main character could be a student preparing for the Olympiad. Since it's about past papers, perhaps the story involves someone finding or accessing exclusive past papers that aren't available to everyone. That could be the inciting incident.

But the box holds no more questions—only a key labeled “Challenge II: The NUS Herbarium.”

Li Wen, recalling her textbook on mutualism, solves it. The lockbox creaks open, revealing a yellowed SJBO 1973 paper.