Official PYQ · 2001Set 1 · Q2.14LTI SystemsMCQ1 mark

GATE EC 2001 Set 1 Q2.14 — LTI Systems

The impulse response functions of four linear systems $\mathrm{S}_{1}, \mathrm{~S}_{2}, \mathrm{~S}_{3}, \mathrm{~S}_{4}$ are given respectively by

$\begin{array}{ll} h_{1}(t)=1 & h_{2}(t)=U(t) \\ h_{3}(t)=\frac{U(t)}{t+1} & h_{4}(t)=e^{3 t} U(t) \end{array}$

Where $\mathrm{U}(t)$ is the unit step function. Which of these systems is time invariant, causal, and stable?

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Answer: D

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Published 10 Oct 2026

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