Index Number of the Last Element of an Array with 9 Elements

To determine the index number of the last element in an array, it is important to understand how arrays are indexed and the concept of zero-based indexing.

Zero-Based Indexing
In many programming languages, including most commonly used ones, arrays are zero-indexed. This means that the first element of an array is assigned an index of 0, the second element has an index of 1, and so on.

Array with 9 Elements
Given that we have an array with 9 elements, we can determine the index number of the last element by subtracting 1 from the total number of elements. In this case, there are 9 elements, so the index number of the last element would be 9 - 1 = 8.

Explanation of the Options
Let's analyze each option provided:

a) 9: This option suggests that the index number of the last element is 9. However, since arrays are zero-indexed, the index numbers range from 0 to n-1, where n is the total number of elements in the array. Therefore, this option is incorrect.

b) 8: This option correctly states that the index number of the last element in an array with 9 elements is 8. This is because the index numbers range from 0 to 8. Therefore, this option is the correct answer.

c) 0: This option suggests that the index number of the last element is 0. However, as mentioned earlier, the first element of an array is assigned an index of 0, not the last element. Therefore, this option is incorrect.

d) Programmer-defined: This option implies that the index number of the last element can be defined by the programmer. While it is possible to define custom indexing schemes in some programming languages, the question assumes the usage of zero-based indexing, which is the standard convention. Therefore, this option is not the correct answer.

Conclusion
The correct answer is option 'B', which states that the index number of the last element of an array with 9 elements is 8. This is because arrays are zero-indexed, and the index numbers range from 0 to n-1, where n is the total number of elements in the array.