Which data structure is characterized by a fixed number of elements of the same data type?

An array is a data structure that is defined by having a fixed size, meaning it can hold a predetermined number of elements. All elements within an array must be of the same data type, which allows for efficient storage and access of data. This characteristic of uniformity in data types enables operations to be performed on all elements without requiring type checks, thus enhancing performance when processing the data.

In contrast, other data structures such as lists, sets, and dictionaries offer different properties. Lists can dynamically change size, allowing for a flexible number of elements which may or may not be of the same type. Sets, while they can hold multiple elements, do not maintain any specific order and inherently allow for unique items only. Dictionaries store key-value pairs, thus allowing for complex data representation but also do not impose a fixed size on themselves. Each of these alternatives does not fit the given definition of a data structure characterized by a fixed number of elements of the same data type, which solidifies why an array is the correct choice.