You are constructing a model of the RNA holoeznyme. You should
A. start with the α subunits and then add the core polymerase consisting of the β β' σ subunits.
B. start with the core polymerase consisting of the β β' subunits and then add the α σ subunits.
C. start with the core polymerase consisting of the β β' σ subunits and then add the α subunit.
D. start with the core polymerase consisting of the α β β' subunits and then add the σ subunit