A marketing manager has developed a regression model to predict quarterly sales of his company's mid$-$weight microfiber jackets based on price and amount spent on advertising. An intern suggests that he include indicator $($dummy$)$ variables for each quarter. Complete parts $($a$)$ through $($c$)$ below.

a$)$ How would you code the variables? $($How many dummy variables do you need? What values would they have?$)$

A$.$ There should be $1$ variable. The values could be $0$ for spring, $1$ for summer, $2$ for fall, and $3$ for winter.

B$.$ There should be $1$ indicator variable for one season. The season chosen does not matter, but it should have a value of $1$ for that season and $0$ for the others.

C$.$ There should be $4$ variables. The variables could be spring $(1$ for spring, $0$ for others$),$ summer $(1$ for summer, $0$ for others$),$ fall $(1$ for fall, $0$ for others$),$ and winter $(1$ for winter, $0$ for others$).$

D$.$ There should be $3$ variables. The variables could be spring $(1$ for spring, $0$ for others$),$ summer $(1$ for summer, $0$ for others$),$ and fall $(1$ for fall, $0$ for others$).$