The answer is:
d.It’s a composite because it’s a mixture of cement, sand, and other granular pieces.
The explanation:
Concrete is a composite, since it is composed of various elements like sand, gravel & water.
Aggregate consists of large chunks of material in a concrete mix, generally a coarse gravel or crushed rocks such as limestone, or granite, along with finer materials such as sand. Cement, most commonly Portland cement, is associated with the general term "concrete.
