Correct Answer: D
Explanation:
In order to calculate the average, or arithmetic mean, of numbers in a set, we add up all of the numbers, then divide that total sum by the n (the count of numbers in the set).
Here we have 86, 90, 88, and 96. This gives us n = 4.
We add up 86 + 90 + 88 + 96 = 360. 360 / 4 = 90.