Concrete is primarily composed of which of the following elements?

Concrete is primarily composed of cement, sand, aggregate, and water. This combination creates a composite material that gains strength and durability as it cures. The cement acts as a binding agent that holds the mixture together, while sand and aggregate (which can include gravel or crushed stone) provide the bulk and strength to the concrete. Water is essential for the chemical hydration process, which allows the cement to harden and bind the components effectively.

The other options do not accurately represent the primary components of concrete. For instance, while clay may be used in some specialized mixtures, it is not a main ingredient in standard concrete. Similarly, lime and silica are more closely associated with other types of construction materials rather than concrete itself. Lastly, soil is not a component of concrete; it may be present in other construction contexts, but it does not contribute to the strength and stability that concrete provides. This makes the correct answer a clear reflection of concrete's true composition.