When two your substances are combined so that each of the pure substances retains its own properties the result is a(n)?
a. mixture
b. isotope
c. element
d. compound

Mixture.

Explanation:

The matter can be classified as:

a) Mixture: Can be homogeneous or heterogeneous.

Mixtures are formed when two or more substances combine and there is no change in the property of the pure substances mixed.

For example:

NaCl and water forms a homogeneous mixture, however on mixing the properties of the two remains the same and they can be separated easily by physical means.

b) Compound: it is formed from two or more elements and this is pure form of matter

c) element: it is the purest form of matter.

Isotopes are the substances which have same atomic number but different atomic mass.