RNA polymerase is the enzyme of transcription and synthesizes RNA using DNA template strand. It is a complex enzyme with five core subunits and a sixth sigma subunit which binds transiently to the core enzyme and positions it to promoters on the DNA. DNA polymerase III is major polymerizing enzyme with ten types of subunits; polymerization and proofreading activities reside in its alpha and epsilon subunits, respectively. The theta, alpha and epsilon form a core polymerase with polymerization activity but lack processivity which is imparted by clamp-loading complex (two copies of tau, gamma, delta and delta prime subunits). DNA and RNA ligases have single subunit. Correct answer is A.