Answer:C
Explanation:
When a constant horizontal force is applied to the box, box started moving in the horizontal direction such that it moves with constant velocity 
Constant velocity implies that net force on the box is zero
i.e. there must be an opposing force which is equal to the applied force and friction force can serve that purpose.
So option c is the correct choice.
Answer:
i am pretty sure you are correct and so sorry if i am wrong i am just trying to help no need to give me anything if i am right but it might be the one abouve the one you chose :) please let me know if i am wrong or right
Explanation:
The study of sound is called sonics and the study of sound waves are acoustics