If the scatter plot between a dependent time series variable and an independent time series variable is curvilinear (curves upward over the data series) what should the forecaster investigate to improve the performance of a linear regression model for the variables?

A. Difference the X data to reduce its value relative to Y.

B. Create a dummy variable that explains the curvilinear relationship.

C. Seasonally adjust the Y variable to remove some of the variation.

D. Use a natural log or other transformation of the X data as a dependent variable.

E. Nothing, just run the regression on the data as it is since it cannot be improved.