According to the situation presented, the explanatory variable is education
An explanatory variable is a term that refers to any factor that can influence the response or outcome of an investigation.
According to the above, education is the explanatory variable because the level of education is a factor that directly influences the result of the research given that the higher the level of education, the higher the incidence of smoking.
According to the above, the correct answer is education (option D).
Learn more in: https://brainly.com/question/10863424