Which of the following is NOT a form of signal coupling between two (2) circuits?

Conductive (galvanic) coupling is a valid mechanism where signals transfer through a direct shared electrical connection, such as a common ground or shared conductor between two circuits.

Inductive coupling is a valid mechanism where a changing magnetic field generated by current in one circuit induces a voltage in an adjacent circuit through mutual inductance.

Reactive coupling is not a defined or recognized form of signal coupling between circuits. The term 'reactive' refers to reactance, an electrical property of inductors and capacitors describing their opposition to alternating current, but reactance is not itself a pathway or mechanism by which a signal transfers from one circuit to another.

Capacitive coupling is a valid mechanism where signals transfer via the electric field across the parasitic capacitance formed between adjacent conductors in two circuits.

Electromagnetic coupling is a valid mechanism where radiated electromagnetic waves emitted by one circuit propagate through space and are received by another circuit.