In illustration 1, if the aircraft's heading turns to the heading marker, what is the outcome concerning joining the selected radial?

The correct outcome regarding joining the selected radial after the aircraft's heading aligns with the heading marker is based on the mechanics of navigating with a VOR (VHF Omnidirectional Range) system. When the aircraft's heading turns to align with the heading marker indicating the selected radial, this signifies that you are approaching or have passed the VOR station itself.

In general, when navigating towards a VOR station, the aircraft will join the selected radial typically after passing over the station. At that point, the radial you are on is considered to be the one selected on the VOR indicator, and the subsequent flight path will allow for navigation along that radial. The relationship between the aircraft's current heading, the VOR navigation setup, and the radial being tracked determines when you'll effectively be on that radial.

Therefore, aligning with the heading marker indicates that the aircraft will indeed be able to join the selected radial after passing the VOR station, which is consistent with how VOR navigation operates.