The correct answer is: A. load current.
The leakage flux is the flux that does not link both the primary and secondary windings of a transformer. It is caused by the leakage inductance of the windings. The leakage inductance is the inductance of a winding that is not shared with the other winding. It is caused by the physical separation of the windings and the presence of air gaps between the windings.
The leakage flux is proportional to the load current. This is because the load current creates a magnetic field that interacts with the leakage inductance of the windings. The greater the load current, the greater the magnetic field and the greater the leakage flux.
The leakage flux does not depend on the voltage or frequency. This is because the voltage and frequency do not affect the leakage inductance of the windings. The leakage inductance is a property of the windings themselves and is not affected by the applied voltage or frequency.
The leakage flux also does not depend on the power factor. This is because the power factor is a measure of how efficiently the load is converting electrical energy into useful work. The power factor does not affect the leakage inductance of the windings and therefore does not affect the leakage flux.