Two coils are said to have mutual inductance when they are linked by:

The concept of mutual inductance is fundamentally based on the interaction of two inductors with a shared magnetic field. When an electric current flows through one coil, it generates a magnetic field, which can induce a voltage in the second coil that is in proximity to this field. This phenomenon occurs due to the principle of electromagnetic induction, where a changing magnetic field in one coil induces an electromotive force (EMF) in the other.

In essence, mutual inductance quantifies the degree to which the magnetic field generated by one coil influences the other coil. The stronger the coupling between the coils and the more significant the overlapping of their magnetic fields, the greater the mutual inductance.

The other choices do not accurately represent the mechanism of mutual inductance. A series wiring connection pertains to how circuits are configured electrically, while a capacitor and an inductor are individual components that do not inherently facilitate the concept of mutual interaction between two separate coils in the context described. Thus, the accurate identification of mutual inductance is indeed linked to the common magnetic field created by their interaction.