Given 2 signals (-3)k u(k) and u (k-1). These two signals are superimposed. This superimposed signal is _______________

• A. \(\frac{z}{z+3} + \frac{1}{z-1}\)
• B. \(\frac{z}{z+3} – \frac{1}{z-1}\)
• C. \(\frac{z}{z-3} + \frac{1}{z-1}\)
• D. \(\frac{z}{z+3} + \frac{1}{z+1}\)