Answer:
Option D: the number of fluoride treatments given to students each month for the last 60 months (range 40-620)
Explanation:
The number of fluoride treatments given to students each month may be graphed with the 60 months on the horizontal axis, using a bar for each month.
The height of each bar will represent the number of fluoride treatments for the month and will be read on the vertical axis.
This histogram will permit to compare visually, in a very easy way, how the number of treatments vary month to month. That is why this is an ideal representation for this kind of data. In other form, it would be harder to compare a set of data for so many months and whose range is so broad (40 - 620).