Correct Option: A

From figure Since, E(s) = X(s) – Y(s).H(s)

or E(s) = X(s) –	G(s)	X(s).H(s)
	1 + G(s) H(s)

or E(s) = X(s) –	1
	1 + G(s) H(s)

	∴ X(s) =	1	for step input
		s

or E(s) =	1		1
	s		+1 (s + 1) × 1/(s2 + 5 + a)(s + 4)

Now, steady state error e_ss is
e_ss = _{t → ∞}lim e(t) = _{t → ∞}lim sE(s)

or ess = s → 0lim ·s	1		1
	s		+1 (s + 1) × 1/(s2 + 5 + a)(s + 4)

or

or ess =	4a
	4a + 1

for steady state error, e_ss to be zero,

4a	= 0
4a + 1

or
a = 0 Hence alternative (A) is the correct choice.