The correct answer is: B. Subscript
A subscript is a number that is used to identify a particular element in an array. For example, in the array arr[0], the subscript 0 identifies the first element in the array.
An array is a data structure that stores a collection of elements of the same data type. The elements in an array are stored in contiguous memory locations, and each element can be accessed by its subscript.
A reference is a pointer to an object. A reference can be used to access the object that it points to.
An ID is a unique identifier for an object. An ID can be used to distinguish one object from another.
In conclusion, the correct answer is: B. Subscript. A subscript is a number that is used to identify a particular element in an array.