Which industry has the highest four-firm concentration ratio?

a. Discount department stores.

b. College bookstores.

c. Cigarettes.

d. Retail gas stations.

There are numerous college bookstores, gas stations and department stores but there are only a few cigarette companies. These companies sell numerous brands of cigarettes but the number of companies and businesses in the cigarette industry is nowhere in comparison with the other industries. The largest four firms in the cigarette industry have the largest market share out of these four industries. The is why the answer is C, cigarettes.