The correct option is B Algae
Melvin Calvin, Andrew Benson, and James A. Bassham elucidated the enzyme catalyzed reaction of photosynthesis in the early 1950s. Exposure of photosynthesizing algae to radioactive carbon dioxide was followed by tracing the fate of a radioactive carbon atom. It was shown that the carbon first binds to a molecule of ribulose 1,5-bisphosphate (RuBP), then immediately splits, forming two molecules of phosphoglycerate (PGA). Thus, the correct answer is A.