The Total Force Needed to Drag a Box at Constant $\mu$

Multiple Choice

The total force needed to drag a box at constant speed across a surface with coefficient of kinetic friction $\mu$ k is least when the force is applied at an angle $\theta$ such that:

A) sin $\theta$ = $\mu$ k.
B) cos $\theta$ = $\mu$ k.
C) tan $\theta$ = $\mu$ k.
D) cot $\theta$ = $\mu$ k.
E) sec $\theta$ = $\mu$ k.