Which bone movement decreases the angle between two bones?

The correct answer is flexion, which is a type of movement that decreases the angle between two bones. This action typically occurs at joints and is commonly observed in movements such as bending the elbow or knee. During flexion, one bone moves closer to another, effectively reducing the angle formed at the joint.

In contrast, extension increases the angle between two bones, such as straightening the arm or leg. Dorsiflexion refers specifically to the upward movement of the foot, decreasing the angle between the foot and the shin, but it is focused on ankle movement. Circumduction involves a circular motion at a joint, where the distal end of a limb moves in a circular path, combining flexion, extension, abduction, and adduction, and does not specifically decrease the angle between two bones at any point. Thus, among the options, flexion is uniquely characterized by the action of decreasing the angle between bones.