The correct option is B PEP
In C4 pathway, the primary carbon dioxide acceptor is phosphoenol pyruvate (PEP) which is present in the mesophyll cells. This is catalysed by PEP carboxylase or PEPcase.
RuBisCo is an enzyme catalysing the fixation of carbon dioxide by ribulose-1,5-biphosphate (RuBP) in C3 cycle.
Pyruvate is the end product of glycolysis.