Concept:The magnetic meridian is defined as the vertical plane that contains the direction of the Earth’s magnetic field at a given location.
Explanation:Imaginary vertical plane passing through the line joining the magnetic north and south poles.
This plane intersects the Earth’s surface along a circle similar to a geographic longitude line.
A freely suspended magnetic needle aligns itself within this vertical plane.
The north pole of the needle points toward the magnetic north pole.
The magnetic meridian at any place is not aligned with the geographic meridian because the Earth’s magnetic axis is tilted relative to its geographic axis.
The angle between the magnetic meridian and the geographic meridian is called magnetic declination.
Declination varies with location — it is larger at high latitudes and smaller near the equator.
Thus, the magnetic meridian is an imaginary vertical plane.
Answer:C. vertical plane