Suppose that a researcher wishes to test for calendar (seasonal) effects using a dummy variables approach. Which af the following regressions could be used to examine this? A regression containing intercept dummies Aregression containing slope dummies A regressioni containing intercept and slope dummies Aregression containing a dummy varlable taking the value 1 for one observation and zero for all others 40. (0, (), and (iv) Me and () only Gand (Monly Kiand only