From the given diagram we can see that, on an average, as the variable x increases, the variable y decreases.
We also know that Negative correlation is a relationship between two variables in which one variable increases as the other decreases, and vice versa.
Thus, from the above two paragraphs it is clear that the graph which shows the cost per day of electricity over a seven-day period, presents, on an average, a Negative Correlation the dependent and the independent variables.