Task: Question Answering
Input (English): Frank needs to move a box by sliding it across the floor. Which two factors will most strongly affect how hard Frank needs to push the box?  
 (A) The density of the box material and the hardness of the floor (B) The thickness of the box material and the hardness of the floor (C) The total mass of the box and the friction between the box and the floor (D) The total height of the box and the distance between his hands and the floor
Output (English): C