Which pennant is hoisted above the National Ensign?

The correct answer is the Church pennant. The Church pennant is flown above the National Ensign to indicate that religious services are occurring on board a vessel. This practice signifies the vessel's commitment to facilitating spiritual welfare, symbolizing a solemn event conducted under the Navy's auspices.

In the context of naval traditions, the placing of the Church pennant above the National Ensign is a respected ritual, as it distinctly communicates the nature of the activity taking place. The National Ensign, representing the nation, remains a constant but is momentarily secondary to the significance of the church service being held.

As for the other options, while they represent various flags or pennants used in naval signaling, they do not fit the specific scenario of being flown above the National Ensign during religious services. Each of those flags has its unique purpose within naval protocol, but the Church pennant is the one specifically associated with indicating an ongoing religious function aboard a Navy ship.