A forest management agency collects measurements from beech trees in a public park. The age of many of the trees is known, and the basal area—the area of land occupied by the trunks of the trees—is also measured. A least-squares equation that compares the basal area to the age of each tree is given by Area hat = 0.439 (age) + 6.226. Based on the residual plot shown, is a linear model appropriate for comparing tree age to basal area?

Because the residuals are centered about zero, a linear model is appropriate.
Because the residual plot does not show a clear pattern, a linear model is appropriate.
Because the residual plot shows a random a scatter of points, a linear model is not appropriate.
Because the residual plot does not appear linear, it is likely that tree age and basal area do not have a linear relationship.