If the number of cigarettes smoked increases, then the risk for lung cancer increases.

correct. so it's TRUE. if this is a true of false question. the more you are exposed to it the more likely you will get it.

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.