Final answer:
Compounds consist of elements in fixed ratios, meaning a compound is made from combining elements in a specific proportion, while elements are pure substances made of only one type of atom.
Step-by-step explanation:
The relationship between elements and compounds can be described as follows: Compounds consist of elements in fixed ratios. This means that a compound is a substance that contains two or more elements chemically combined in a specific proportion. For example, water (H2O) is a compound made up of two hydrogen atoms for every one oxygen atom. Elements, on the other hand, are pure substances that are made up of only one type of atom and cannot be broken down into simpler substances through chemical means.
Contrary to the relationships among elements, compounds, and mixtures, elements are not composed of compounds nor are elements and compounds forms of mixtures. Mixtures are combinations of two or more pure substances that retain their individual properties and can be separated physically. Therefore, the correct answer to the relationship between elements and compounds within pure substances is C) Compounds consist of elements in fixed ratios.