You are given a science question (easy-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.

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
C