When all primary AC power is gone, the aircraft must rely on emergency power from the batteries to keep the essential systems running. The batteries are sized to support those critical loads for a fixed period, which in this scenario is 30 minutes. That half-hour window gives the crew enough time to maintain basic flight capability, verify status, and complete a safe approach and landing while the situation is stabilized. The other durations would require a different battery capacity or load mix, but with five AC generators lost, the design expectation is to provide approximately 30 minutes of emergency power for the necessary avionics, instruments, communications, and emergency lighting.

The main idea is recognizing MSS-exclusive, stand-alone equipment rather than components tied into the aircraft’s primary flight/navigation system. The EGI 3 is an Embedded GPS/Inertial unit that can be used as a separate MSS-specific module, kept independent from the aircraft’s main flight and navigation architecture. Its placement below the flight deck jump seat fits a setup where MSS hardware is nearby but not integrated into the cockpit’s flight/navigation loop, allowing MSS personnel to operate without affecting the aircraft’s standard systems. The other devices are typically associated with the core flight/navigation suite or used for broader aircraft systems, so they wouldn’t meet the requirement of being exclusive to the MSS and not integrated with the flight/navigation system.

The main idea is identifying which transformer-rectifier units actually feed the SME DC busses. Transformer-rectifier units convert AC power into the DC that powers the busses, and the diagram shows which TRs are connected to each DC bus. In this system, the SME DC busses are connected to the outputs of TR 5 and TR 6, making them the DC power sources for those busses. This pairing provides redundancy and ensures a stable DC supply to the SME busses. The other transformer-rectifier units (TR 1 and 2, TR 3 and 4, TR 7 and 8) are wired to different busses or parts of the system and do not energize the SME DC busses, so they are not the correct sources for those busses.

The key idea is that the UHF MILSATCOM uplink is a shared, single-channel path. On MILSATCOM, the ground and airborne links use one transmitter path to reach the satellite, and multiple ARC-210 radios connected to that uplink cannot all transmit at the same time without causing interference and signal collisions. To keep the link clean, only one radio is allowed to transmit on the UHF MILSATCOM channel at any given moment, while the others can receive or operate on other bands. So, the best answer is that only one ARC-210 can transmit simultaneously on UHF MILSATCOM. The other options would create uplink conflicts that the system is designed to avoid.