Which of the following represents the polar modulus of the hollow shaft?
[ If Do = External diameter and Di = Internal diameter ]
1
[ 16π/Do ] [ \({Do}^4 - {Di}^4\) ]
2
[ π/16Do ] [ \({Do}^3 - {Di}^3\) ]
3
[ π/16Do ] [ \({Do}^4 - {Di}^4\) ]
4
[ 16/πDo ] [ \({Do}^4 - {Di}^4\) ]