This question is actually concerned about the ecosystem created within the jar as well. For 2m, it can be explained as such:
All living things need air, food and water to survive. [necessary concept]
The transparent container allows sunlight to pass through, so the plant could photosynthesize. This allows it to produce oxygen and food needed for survival. [1m]
The air-tight cork prevents water vapour from escaping the bottle. The water vapour produced by the living things condenses on the glass, thus providing water for the plant to survive. [1m]
It is not specified in the question, but the snail is likely to have died due to insufficient oxygen. It’s a good question though, and would likely come out in some form for PSLE.
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