Choose the one best answer. Briefly explain your reasoning.

Suppose you want to estimate a model that will allow you to test the effect of being a pot smoker (pot=1) and a drinker (drink=1) on the number of sexual partners (partners) an individual has had. The best model to estimate would be:

a) partners =0 +1pot +2drink + u

b) partners =0 +1pot *drink + u

c) partners =0 +1pot +2drink +3pot*drink + u

d) partners =1pot *drink + u