5.4 Lurking variables. People who attend church or synagogue are less likely to smoke or be overweight than nonattenders. In the study described in Exercise 5.2,
(a) smoking is a lurking variable, but weight is not.
(b) weight is a lurking variable, but smoking is not.
(c) smoking and weight are both lurking variables.
(d) neither smoking nor weight is a lurking variable.