Which of the following is true about the impulse response of a system?

A) It is the output of the system when the input is a sine wave.

B) It represents the system's behavior over time when excited by a delta function.

C) It is always periodic.

D) It only applies to FIR filters.

Answer: B) It represents the system's behavior over time when excited by a delta function.

Explanation: The impulse response of a system is its output when the input is an impulse (delta function). It characterizes how the system responds to any arbitrary input through convolution.