Which of the signals/systems are non-causal in nature? (A) y(n) = x(n^2) (B) y(n) = (0.4)^n x(n) (C) y(n) = [x(n) + x(n - 1) + x(n + 1)]/3 (D) y(n) = x(n) + x(n - 4)
- A. Only (A)
- B. (A) & (C)
- C. (B) & (D)
- D. Only (B)
Answer: B. (A) & (C)
Explanation: y(n) = x(n²) depends on future input for n > 1 (e.g. y(2) = x(4)), and y(n) in (C) depends on x(n+1), making both (A) and (C) non-causal.