The time taken by a body in sliding down a rough inclined plane of angle of inclination \[45{}^\circ \] is n times the time taken by the same body in slipping down a similar frictionless plane. The coefficient of dynamic friction between the body and the plane will be

• A. \[1/(1-{{n}^{2}})\]
• B. \[1-(1/{{n}^{2}})\]
• C. Ö\[\left\{ 1-(1/{{n}^{2}}) \right\}\]
• D. Ö\[\left\{ 1/(1-{{n}^{2}}) \right\}\]