The issue is identified as a media negotiation problem, which can often be due to insufficient bandwidth allocation between regions. The exhibit shows that regions A and B have a very low bandwidth allowance (kbps=8). Increasing the bandwidth allowance between the RTP_Reg and SJ_Reg regions to 64 kbps is likely to resolve the issue as it ensures enough bandwidth for the calls to be successfully negotiated and established. While modifying codec preferences (option C) might seem appropriate, it won't be effective if the fundamental bandwidth allocation is too low to support the chosen codecs. Therefore, increasing the bandwidth allocation is the most direct and effective solution.