The odd one out is C. Sand.
Brick, cement, and wall are all building materials, while sand is not. Sand is a granular material composed of finely divided rock and mineral particles. It is used in a variety of construction applications, including concrete, mortar, and plaster.
Brick is a rectangular block of clay or other material that is used in building. It is typically fired in a kiln to harden it. Bricks are often used to build walls, fireplaces, and chimneys.
Cement is a binding agent that is used to hold together other materials, such as sand and gravel. It is made from limestone, clay, and sand that are heated and ground into a powder. Cement is mixed with water to form a paste that is used to make concrete.
Wall is a vertical structure that is built to enclose an area or to provide support. Walls are typically made of brick, stone, concrete, or wood. They can be used to protect people and property from the elements, to provide privacy, or to define boundaries.