Substances that make up a mixture their own properties once they are combined to form a mixture. . i need to study for finals.

I believe the answer to this is;
Substances that make up a mixture RETAIN their own properties once  they are combined to form a mixture. 
    I believe the answer is RETAIN because the combination in question is a MIXTURE. A mixture is a combination of various substances. In the case of mixtures, all the substances retain their own properties. That is; they remain the way they are and do not change. An example of a mixture is air. And to prove that air is a mixture;
The components of air retain their individual properties.
The components of air cannot be represented by a chemical formula
When the components of air combine, they do not show any form of chemical change, like heat release, change in pressure
  Hope i helped, have a nice day.

Cis the

D. is the answer hope that you