Explanation: INMARSAT-B was a foundational global mobile satellite system, offering real-time, circuit-switched services for maritime, land, and aeronautical users. Option A correctly identifies its key capabilities: digital voice at 16 kbps, Group 3 fax at 14.4 kbps, and high-speed duplex data at 64/56 kbps. These rates represented a significant improvement over earlier satellite systems, providing robust and higher-capacity communication. Option B is incorrect because INMARSAT-B primarily offered real-time services, not store-and-forward, and the rates listed are not accurate for its main data offerings. Option C lists rates more typical of slower, older systems or refers to analog bandwidth, not the digital capabilities of INMARSAT-B. Option D is misleading; while INMARSAT satellites use spot beams for efficiency, INMARSAT-B provided broad global (non-polar) coverage, and this statement does not describe the *services* themselves.