A block has been placed on an inclined plane. The slope angle 6 of the plane is such that the block slides down the plane at a constant speed. The coefficient of kinetic friction is equal to

• A. \[\sin \,\,\theta \]
• B.  \[\cos \,\,\theta \]
• C.  \[g\]
• D.  \[\tan \,\,\theta \]