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The transfer function of a plant is $T(s)=\frac{5}{(s+5)\left(s^{2}+s+1\right)}$. The second-order approximation of $T(s)$ using dominant pole concept is

1. $\frac{1}{(s+5)(s+1)}$
2. $\frac{5}{(s+5)(s+1)}$
3. $\frac{5}{s^{2}+s+1}$
4. $\frac{1}{s^{2}+s+1}$