The correct answer is B. True power.
Apparent power is the product of the voltage and current, without regard to the phase angle between them. True power is the product of the voltage and current, taking into account the phase angle between them. Reactive power is the product of the voltage and current, but it is not real power because it does not produce any work.
When an alternating current passes through an ohmic resistance, the electrical power converted into heat is true power. This is because the voltage and current are in phase, so the product of their magnitudes is the real power.
Apparent power is the product of the voltage and current, without regard to the phase angle between them. This means that apparent power can be greater than or less than true power, depending on the phase angle.
Reactive power is the product of the voltage and current, but it is not real power because it does not produce any work. This is because reactive power is due to the inductive or capacitive reactance of the circuit, which causes the current to lag or lead the voltage.
Therefore, the correct answer is B. True power.