A heavy box sits on the floor and does not move. The force preventing it from sliding when pushed gently is:

FRICTION is the force that resists the sliding motion between the box and the floor, preventing it from moving when pushed gently. ASVAB Mechanical Comprehension tests forces. FRICTION opposes motion between surfaces in contact; STATIC friction holds an object still until enough force overcomes it; KINETIC friction acts on a moving object. Other forces: GRAVITY (pulls down); TENSION (pull through a rope/cable); NORMAL force (surface pushing up). Friction resisting the push is the relevant force here — a commonly tested concept.