Phasor:
A phasor is a mathematical representation of a sinusoidal waveform that is used to simplify the analysis of electrical circuits and systems. It is a complex quantity that represents the magnitude and phase of an alternating current or voltage.

Statements:
a) It may be a scalar or a vector.
b) It is a time-dependent quantity.
c) It is a complex quantity.
d) All are true.

Explanation:
a) It may be a scalar or a vector:
- This statement is not true. A phasor is always a vector quantity. It represents the magnitude and phase of a sinusoidal waveform. Scalars only have magnitude, while vectors have both magnitude and direction. Since a phasor represents both magnitude and phase, it is always a vector.

b) It is a time-dependent quantity:
- This statement is true. A phasor represents an alternating current or voltage, which varies with time. The phasor concept allows us to analyze the steady-state behavior of a sinusoidal waveform by representing it as a single complex number.

c) It is a complex quantity:
- This statement is true. A phasor is a complex number that consists of a real part and an imaginary part. The real part represents the magnitude or amplitude of the waveform, while the imaginary part represents the phase or angle of the waveform. The complex nature of phasors allows for easy mathematical operations such as addition, subtraction, multiplication, and division.

d) All are true:
- This statement is not true. As discussed above, statement a) is not true. Therefore, all the statements are not true.

Conclusion:
The statement that is not true of a phasor is option 'A' - It may be a scalar or a vector. Phasors are always vector quantities that represent the magnitude and phase of a sinusoidal waveform.