Suppose You Fit a (Linear or Nonlinear) Trend Regression to a Monthly

Multiple Choice

Suppose you fit a (linear or nonlinear) trend regression to a monthly time series and discover that the R² is only 18 percent. The best conclusion is that:

A) adding seasonal factors might make things worse.
B) fitting a seasonal component could raise the R².
C) there is no seasonality in the time series.
D) the overall trend is probably negative.