Which statement best defines a deterministic signal?

• A. Completely specified as a function of time.
• B. Only defined at discrete times.
• C. Has finite energy.
• D. Repeats after a fixed period.

Answer: (A)

Deterministic signals are fully described by a precise rule that assigns a unique value to every time instant. If you know the time, you can compute the exact value of the signal with no randomness involved. That idea is captured by saying the signal is completely specified as a function of time.

The other descriptions refer to different properties. Being defined only at discrete times speaks to a discrete-time representation, not to how completely the signal is defined over all time. Finite energy is about how much total energy the signal has, which is a separate attribute from determinism. Repeating after a fixed period describes periodicity, which is not required for a signal to be deterministic.