Is the data set approximately periodic? if so, what are its period and amplitude?

The data set is roughly periodic, you can see the data that follows a pattern. For example, data point 1 is (1, 102), the 5 is (5, 98) and 9 is (9, 100).
 Every 4 periods, the values resemble each other.
 The same can be shown with the point (2, 76) and the point (6, 74) and (10, 75).
 Therefore, it can be concluded that the period is 4 and the amplitude approximately 25.
 Finally, the correct option is the third.
 Period 4 and approximate amplitude of 25