The block diagram of a system is shown in the figure

If the desired transfer function of the system is $\frac{C(s)}{R(s)}=\frac{s}{s^2+s+1}$ then $G(s)$ is

1. $1$
2. $s$
3. $1/s$
4. $\frac{-s}{s^3+s^2-s-2}$

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