Final answer:
The missing element in the program written by the programmer is a loop condition.
Step-by-step explanation:
The missing element in the program written by the programmer is a loop condition.
In order to calculate the average of a list of numbers, the program needs to iterate over each number in the numberList and sum them up. This requires a loop condition to control the iteration.
Without a loop condition, the program will not be able to properly calculate the average.