Acompound differs from a mixture because it a. always remains frozen even at high temperatures. b. is formed from two cations. c. always contains the same elements in the same proportion. d. can form only in the presence of heat energy.

The correct option is C

Explanation:

A compound is a substance that contains two or more atoms that are chemically combined. They can be represented using chemical symbols. Examples are NaCl, CH4, HBr and CaCl2

A mixture is a combination of different substances that are physically combined, They cannot be represented using chemical symbols. Examples are crude oil, air and blood

For a particular mixture, once the constituents are present regardless of varying proportions, the mixture remains the same, with the same name. For instance, if two unknown samples labelled A and B contain red blood cells, white blood cells and platelets in different proportions, they will both be regarded as blood however, for a particular compound, constituents must be in the same proportion in order to be regarded as that compound. For instance, carbon monoxide (CO) will always contain one atom of carbon and one atom of oxygen - if the number of oxygen atom increases to two, the substance becomes a different compound called carbon dioxide (CO2).

Hence,  a compound must always contain the same elements in the same proportion while a mixture can contain the same constituents in different proportions.

b.final