Which of the following relations is true?

The possible value of Poisson's ratio is

$A$ steel wire of length $2 \ m$ and Young's modulus $2.0 \times 10^{11} \ N/m^2$ is stretched by a force. If Poisson's ratio and transverse strain for the wire are $0.2$ and $10^{-3}$ respectively,then the elastic potential energy density of the wire is . . . . . . $\times 10^5 \ J/m^3$.

$A$ tension of $20 \,N$ is applied to a copper wire of cross-sectional area $0.01 \,cm^2$. The Young's modulus of copper is $1.1 \times 10^{11} \,N/m^2$ and the Poisson's ratio is $0.32$. The decrease in the cross-sectional area of the wire is:

The relationship between Young's modulus $Y,$ Bulk modulus $K,$ and modulus of rigidity $\eta$ is:

The Young's modulus of the material of a wire is $6 \times 10^{12} \ N/m^2$ and there is no transverse strain in it,then its modulus of rigidity will be