Two Firms (A and B)have Marginal Costs MC_A and MC_B,marginal

Two firms (A and B) have marginal costs MC_A and MC_B,marginal revenues MR_A and MR_B,and market marginal revenue MR.If both firms produce as a cartel,they should produce so that:

A) MC_A = MC_B = MR.
B) MC_A = MR_A and MC_B = MC_B.
C) MC_A + MC_B = MR.
D) MC_A + MC_B = MR_A + MR_B, not necessarily MC_A = MR_A.
E) MC_A = MC_B = MR_A + MR_B.