Final answer:
G3P is used by plants in the Calvin cycle for several purposes, but it is not involved in the formation of RuBP from G3P molecules.
Step-by-step explanation:
The product of the Calvin cycle, G3P (glyceraldehyde-3-phosphate), is used by plants for various purposes, including the formation of carbohydrate molecules and the regeneration of RuBP.
However, it is not used for the formation of RuBP from G3P molecules. Instead, the formation of RuBP is part of the Calvin cycle itself, which uses energy in the form of ATP and NADPH to reduce CO₂.