12. Suppose a positive relationship had been found between each of the following sets of variables. In Section 11.3, seven potential reasons for such relationships are given. Explain which of the seven reasons is most likely to account for the relationship in each case. If you think more than one reason might apply, mention them all but elaborate on only the one you think is most likely.

a. Number of deaths from automobiles and beer sales for each year from 1950 to 1990.

b. Number of ski accidents and average wait time for the ski lift for each day during one winter at a ski resort.

c. Stomach cancer and consumption of barbecued foods, which are known to contain carcinogenic (cancer-causing) substances.

d. Self-reported level of stress and blood pressure.

e. Amount of dietary fat consumed and heart disease.

f. Twice as many cases of leukemia in a new high school, built near a power plant, than at the old high school.