Human Anatomy

Step 1: Understand the types of joints.
The ball-and-socket joint is one of the most mobile types of joints.
It consists of a spherical ball-like structure at the end of one bone fitting into a cup-like socket of another bone.

Step 2: Identify the location of a ball-and-socket joint.
The ball-and-socket joints are located in the shoulder and hip.
They allow for rotational movement and movement in almost all directions.

Step 3: Analyze the options.
The shoulder joint is a ball-and-socket joint, where the ball-shaped head of the humerus fits into the socket of the scapula.
The knee joint is a hinge joint, not a ball-and-socket joint.
The atlas is part of the cervical vertebrae and doesn't form a ball-and-socket joint.
The cranium (skull) houses immovable joints called sutures, not a ball-and-socket joint.

Conclusion: The correct answer is (A) Shoulder.