Final answer:
The initial product of carbon fixation in the Calvin Cycle contains 6 carbons, which quickly breaks into two 3-carbon molecules, thus the correct answer is A. 6, 3. In the cycle, 8 G3P are made and 1 G3P is exported when four CO2 molecules enter.
Step-by-step explanation:
The initial product of carbon fixation in the Calvin Cycle contains 6 carbons. However, this 6-carbon compound is unstable and immediately breaks down into two molecules containing 3 carbons each. Therefore, the correct answer to the question is: A. 6, 3.
Moreover, during the Calvin Cycle, for every four molecules of carbon dioxide that enter the cycle, eight molecules of glyceraldehyde-3-phosphate (G3P) are produced. However, since the cycle's main goal is to regenerate RuBP and continue the cycle, only one of these G3P molecules can be exported at a given time for the synthesis of glucose. Thus, when four molecules of carbon dioxide enter the Calvin cycle, the result is 8 G3P made, 1 G3P exported. This is essential for the synthesis of sugars like glucose.