EXPLANATION :
a. Data set that shows NO relationship between two variables.
The data will be scattered without having a linear or definite shape.
From the options, it is Figure 2
b. Data set that shows a negative linear relationship between two variables.
Negative linear relationship implies a downward direction in a shape of a line.
From the options, it is Figure 1
c. Data set that shows a positive linear relationship between two variables.
Positive linear relationship implies an upward direction in a shape of a line.
From the options, it is Figure 4
d. Data set that shows a nonlinear relationship between two variables.
There is a definite shape but it is not in a shape of a line.
From the options, it is Figure 3