Final answer:
A compound is a substance made up of two or more different elements combined in a fixed ratio, fitting the provided definition of something characterized by the combination of its parts.
Step-by-step explanation:
The student's question is asking to identify something that is characterized by being a combination of its parts. The correct answer is a compound because it perfectly fits the definition provided, which is 'A substance made up of two or more different elements that are joined together in a fixed ratio.' Therefore, the general quality or character of such a substance can be regarded as its compound nature. This excludes the other possible answers since they either do not combine elements in a fixed ratio (B. heterogeneous mixture, E. homogeneous mixture) or are not composed of multiple elements (C. metal alloy, D. element).