In a mixture of the five proteins listed below, which should elute second in size-exclusion (gel- filtration) chromatography?

A) cytochrome c M_r = 13,000
B) immunoglobulin G M_r = 145,000
C) ribonuclease A M_r = 13,700
D) RNA polymerase M_r = 450,000
E) serum albumin M_r = 68,500