Question $8\mathrm{.}42-$ A hollow thin$-$wall steel pipe has its mean diameter of $30$ cm and wall thickness of $10$ mm $.$ If maximum allowable shear stress in its cross$-$section is $5$ Mpa $,$ the maximum torque $(kN-m)$ can be applied to the pipe is most nearly:

A$.2$

B$.20$

C$.200$

D$.2,000$