Question 1:
The answer is set C.
A nonlinear relationship is a type of relationship between two entities in which change in one entity does not correspond with constant change in the other entity. This might mean the relationship between the two entities seems unpredictable or virtually absent.
A negative nonlinear relationship means the slope is negative OR as the x value increases, the y values decrease.
In the above options, set C is the only table that agrees to the the conditions above and hence, it is the answer.
If you were to actually plot a graph of set C, it would clearly show a negative nonlinear graph.
Question 2:
A line of best fit is a straight line drawn through the center of a group of data points plotted on a scatter plot.
To do that, we need the end points to be clear since the line of best fit will have to start and end there.
In all the options, B is the only one that is close to the end point and therefore can pass as the end points.
Hence, the answer is B.
Question 3:
A line of best fit is a straight line drawn through the center of a group of data points plotted on a scatter plot.
Hence, the answer is A.