A continuous signal is defined for:

A continuous signal is defined for:

• A. Only at discrete times.
• B. Only for t ≥ 0.
• C. All time values.
• D. Only when energy is finite.

Answer: (C)

Continuous-time signals are functions of a continuous time variable, meaning they have a value x(t) for every instant t in their time domain. This is why the statement that a continuous signal is defined for all time values is correct: you specify a value at every time point within its domain (often all real numbers, or a given interval).

The other ideas don’t fit the general concept: a signal defined only at discrete times describes a discrete-time signal, not continuous-time. A signal restricted to t ≥ 0 is still a valid continuous signal, but it’s not required to be defined only there; it could exist for negative times as well. Finite energy is not a defining requirement, since many continuous signals (like a sinusoid or a constant) have infinite energy over all time.