For making a scatter plot of the data set which would be the best scale and interval for the axis that represent the amount of fluorine?
a.2 to 10 with intervals of 1
b.4 to 10 with intervals of 2
c.0 to 8 with intervals of 0.2
d.0 to 8 with intervals of 4

Looking at the values given for Flouride (mg), we have the lowest value of 0.4 and the highest value of 7.1

The axis should start at 0 and the least number it should go up to is 8

Looking at the values in between 0.4 and 7.1, we have 1.6, 2.5, 3.1, 4.5 and 6.8
Ideally, we want the scale that makes it easier to read this values, the smaller the scale is the better. 

0 to 8 with intervals of 0.2 (C)