Which managed care plan REQUIRES members to select a primary care physician who must provide referrals to see in-network specialists?

Why this is the answer

An HMO (Health Maintenance Organization) operates on a gatekeeper model: the member chooses a primary care physician (PCP) who coordinates all care and must issue referrals before the member can see specialists. Care outside the HMO network is generally not covered (except emergencies). A PPO (Preferred Provider Organization) allows members to see any provider without a referral, though in-network providers cost less via negotiated rates. HRAs and HSAs are account-based funding mechanisms, not managed care networks. Texas HMOs are licensed under TIC Chapter 843, and TIC Chapter 1271 governs their evidence of coverage. The TX outline §V.C identifies both HMO and PPO as distinct medical expense insurance types.