What materials are combined in the making of mortar?

The process of making mortar involves combining cementitious materials, sand, and water. Cementitious materials, such as Portland cement, serve as the binding agent that gives mortar its strength and durability. Sand provides the necessary bulk and workability, allowing the mortar to be applied effectively between bricks or blocks. Water is crucial as it facilitates the chemical reactions that occur when the cement hydrates and allows the mortar to reach its designed strength.

In contrast, other combinations listed, such as gravel in the first option, are more common in concrete mixes rather than in mortar, which requires a finer aggregate for optimal performance. Options including clay do not accurately describe mortar's composition, as clay is not typically used in modern mortar formulations. Additionally, while limestone might be present in some cement products, it is not a standard component of mortar itself. Therefore, the correct answer encompasses the essential materials specifically used in mortar preparation.