Using construction data from October of 2012 to September 2022, assuming unemployment has been decreasing over the last 10 years, but that changes from month to month, what time variables should be included in a time series regression to forecast the hours worked by construction workers in October 2023. (Mark all that applies) a. A time variable (t = 1 for October 2012, t = 2 for November 2012,...) Correct Answer b. Month variables (Feb, Mar, ..., Dec) c. Month variables (Jan, Feb, ..., Dec) Correct! d. A time variable (t = 0 for October 2012, t = 1 for November 2012,...)