Use the vertical line test to determine if the above graph is a function or not.

It is a function.  There is nowhere on the graph where the vertical line passes through the graph more than once.

I believe that the answer would be D, there is a relationship between price and gift baskets sold, and the relationship is that as the price increases, the gift baskets sold decreases. 

Despite the fact that there is an outlier, the point representing the 80 gift baskets sold at $52, there is still a pattern which shows that as the price of the baskets increases, the number of sales decreases based on the other points.