Final answer:
The box will slide down the plank.
Step-by-step explanation:
When an object slides down an inclined plane, the force of friction opposes its motion. The coefficient of friction, denoted as μ, determines the amount of friction between the object and the plane. In this case, we have the kinetic and static coefficients of friction, μk and μs respectively.
If the box is sliding down the plank, it means that the force of friction, which is given by μk times the normal force, is less than or equal to the force component down the plane, which is given by mgsin(θ). Therefore, the answer is option A: The box will slide down the plank.
The answer does not depend on the value of μs, as the static coefficient of friction is only relevant when the box is at rest and not sliding down the plank.