How does manual reversion operate in the aircraft system?

Manual reversion in aircraft systems primarily involves a process where the flight controls can still be operated by the pilot even if certain electronic or hydraulic systems fail. In this mode, the aircraft's design allows control inputs to be transmitted through alternative means, often utilizing mechanical linkages such as cables attached to primary control surfaces.

The correct answer highlights that during manual reversion, operations rely on physical connections, such as cables running through the Power Control Units (PCUs), to achieve control of the aircraft. This is crucial in ensuring that pilots maintain control when automated or primary systems become inoperable. This capability ensures redundancy and safety in flight operations, allowing pilots to intercede directly when required.

The other options either suggest mechanisms that are not applicable to manual reversion or misrepresent how control is maintained in such scenarios. For instance, suggesting that it's purely automatic would overlook the necessity of pilot input, especially in critical situations. The reliance on hydraulic assistance or electrical controls does not capture the fundamental nature of manual reversion, which is centered around maintaining direct physical control of the aircraft without dependence on those systems.