Consider the following practices when comparing SES, Holt and Holt-Winters models on monthly warehouse shipment data.

I. Using chronological training and testing periods preserves the forecasting order.

II. A model with lower training RMSE must also have lower test RMSE.

III. A model with lower MAE can nevertheless have higher RMSE than another model.

IV. Seasonality should be determined entirely by whichever model has the most parameters.

Choose the correct combination.