Which of the following is true of the "linear regression" forecasting method? 1. linear regression is the most popular of all forecasting methods. 2. the amount of historical data required is typically in the range of 10-20 observations, though more is genrally preferred. 3. the data pattern can allow for stationarity. 4. seasonality in the data cannot be accomodated. 5. a trend in the data can also be spotted, but that trend must be non-linear. 6. the forecast horizon can range from short to medium. 7. a trend in the data can also be spotted, but that trend must be linear.