Correct Answer - Option 2 : 3/√ρ
The resistance of the wire in terms of resistivity is given as
\(R\; = \;\frac{{\rho l}}{A}\; = \;\frac{{\rho l.l}}{{A.l}}\; = \;\frac{{\rho {l^2}}}{V}\; \Rightarrow \;{l^2}\; = \;\frac{{RV}}{\rho }\; = \;\frac{9}{\rho }\; \Rightarrow \;l\; = \;\frac{3}{{\sqrt \rho }}\)