Understand the definitions of the terms: an element is a pure substance made of only one type of atom; a compound is a substance formed when two or more different elements chemically bond together; a mixture is a physical combination of two or more substances; and a solution is a homogeneous mixture of two or more substances.
Identify the composition of water: water (H\_2O) consists of hydrogen and oxygen atoms chemically bonded together in a fixed ratio.
Since water is made of two different elements chemically combined, it fits the definition of a compound rather than an element, mixture, or solution.
Note that although water can be part of a solution (like saltwater), water itself is not a solution but a pure compound.
Conclude that the correct classification for water is a compound.