4.Consider the following three systems, where [n] or x(t) is the system input, y[n] or y(t) denotes the system output, and I.
Which of the following statements is correct?
(A) I is time-invariant, II is linear, Ill is causal.
(B) I is memoryless, II is causal, III is nonlincar.
(C) I is stable, II is linear, III is memoryless.
(D) I is causal, II is memoryless, III is linear.
(E) None of the above statements are correct.