Which of the following proteins is most abundant on the earth?

The correct option is B RuBisCO
The carbon dioxide acceptor in Calvin cycle is ribulose 1, 5 bisphosphate (RUBP). During the initial carboxylation phase of calvin cycle, six molecules of carbon dioxide combine with six molecules of RUBP to form twelve molecules of 3, Phosphoglyceric acid (3-PGA), which is the first stable product of the cycle. This reaction is catalyzed by the enzyme Ribulose bisphosphate carboxylase, usually referred to as RuBisCO. This enzyme is the most abundant protein on earth. It occurs in all the green parts of actively photosynthesizing plants.