Metal oxides are compounds composed of a metal element bonded with oxygen. When these metal oxides react with water, they undergo a chemical reaction that produces a basic solution. This means that the resulting solution will have a pH greater than 7, indicating the presence of hydroxide ions (OH-) which are characteristic of bases.

The reaction between metal oxides and water is known as a hydrolysis reaction. During this reaction, water molecules break apart and react with the metal oxide to form metal hydroxide compounds. The general equation for this reaction is:

Metal oxide + Water → Metal hydroxide

For example, when calcium oxide (CaO) reacts with water, it forms calcium hydroxide (Ca(OH)2):

CaO + H2O → Ca(OH)2

In this reaction, the water molecule splits into hydrogen ions (H+) and hydroxide ions (OH-). The hydroxide ions then combine with the metal cations from the metal oxide to form metal hydroxides. The resulting solution will have a basic pH due to the presence of the hydroxide ions.

Metal hydroxides are considered bases because they can accept protons (H+) from acids to form water and a salt. Bases are substances that can donate hydroxide ions (OH-) or accept protons (H+). In the case of metal hydroxides formed from the reaction of metal oxides with water, they release hydroxide ions into the solution, making it basic.

In summary, metal oxides react with water to form metal hydroxides, which are bases. The hydrolysis of metal oxides with water results in the release of hydroxide ions, giving the resulting solution a basic pH. Therefore, the correct answer is option 'C' - bases.

When metal oxides react with water then it forms metal hydroxide which is a base.