The Regeneration Phase of the Dark Reactions Are Best Considered

The regeneration phase of the dark reactions are best considered in terms of regenerating 6 molecules of ribulose-1,5-bisphosphate, a process that requires 6 ATP. Considering the number of photons required for production of ATP in the light reactions, on average, how many photons must be absorbed for each molecule of ribulose-1,5-bisphosphate regenerated?

A) 1.5
B) 3
C) 4.5
D) 6
E) 9