Final answer:
The molecule that must enter the Calvin cycle continually for the light-independent reactions to take place is RuBP
Step-by-step explanation:
The molecule that must enter the Calvin cycle continually for the light-independent reactions to take place is b. RuBP (ribulose-1,5-bisphosphate). RuBP is a five-carbon sugar molecule that reacts with carbon dioxide to initiate the Calvin cycle. Without RuBP, the fixation of carbon dioxide and the subsequent production of glucose would not occur.