The correct option is A RUDP or RUBP
During the dark phase of photosynthesis, carbon dioxide combines with RUBP or RUDP (ribulose bi/di phosphate) in the carboxylation reaction catalyzed by enzyme RUBISCO (ribulose-1,5-bisphosphate carboxylase/oxygenase). The carboxylation of RUBP generates 3 PGA or 3 phosphoglyceric acid, which is the first stable product of dark phase.