Which of the Following Begins the Calvin Cycle That Results

Which of the following begins the Calvin cycle that results in the entire pathway being carried out under environmental conditions?

A) 3PG is reduced to G3P using ATP and NADPH + H⁺.
B) RuBP is regenerated.
C) CO₂ and RuBP join forming 3PG.
D) G3P is converted into glucose and fructose.
E) Any of the above; as a cycle, it can start at any point.