The Solution:
Given:
We are asked to determine the period of the given data.
Clearly, it is aperiodic data because it decreases and then increases and keeps repeating the pattern at an approximate period of 4.
observe, from 1 to 4, it decreased. But from 5 to 9, it increased.
So, at every interval of 4, it keeps repeating the pattern.
Therefore, the correct answer is 4.