Final answer:
The scatterplot shows that as the length of a call increases, the cost of the call also increases.
Step-by-step explanation:
The scatterplot shows the relationship between the length of an international long-distance phone call and its cost. By observing the scatterplot, we can see that as the length of a call increases, the cost of the call also increases. This can be concluded because the points on the scatterplot are generally moving in an upward direction. Therefore, the best-supported conclusion is:
a) As the length of a call increases, the cost of the call increases.