SOLUTION
The dot plot with the greatest variability is the one with the most spread or with the largest range.
A is between 6 to 9, that is 3
B is between 6 to 11, that is 5
C is between 31 to 34, that is 3
D is between 52 to 58, that is 6
So plot D has the greatest variability
Hence the answer is option D