The Young's modulus of steal is 210 GPa. Its poissions ratio is 0.3. Then its rigidity modulus is 

Given,

Youngs modulus $\mathrm{Y}=210\mathrm{Gpa}$

Poisons ratio $\mathrm{\sigma }=0.3$

We know that,

$\mathrm{Y}=2\mathrm{\eta }(1+\mathrm{\sigma })$

$\mathrm{\eta }=\frac{\mathrm{Y}}{2(1+\mathrm{\sigma })}$

$\mathrm{\eta }=\frac{210}{2(1+0.3)}$

$\mathrm{\eta }=80.8\mathrm{GPa}$

Hence the correct answer is 80.8 GPa.