A researcher conducts multiple logistic regression to examine coffee intake (cups/day) and bladder cancer, also including smoking status (never, past, current) in the model. Smoking is associated with both coffee intake and bladder cancer and the odds ratio between coffee intake and bladder cancer decreases when smoking status is included in the model. In this scenario what would "smoking status" be:

a.

Response variable

b.

Effect modifier

c.

Confounder