Which of the following is a single product line?
a. Four-door sedans offered by various automobile manufacturers
b. Passenger jets manufactured by Airbus and Boeing
c. Almond, caramel and dark chocolate flavors of Hershey Kisses
d. Different brands of toothpaste for people with sensitive teeth
Answer: c. Almond, caramel and dark chocolate flavors of Hershey Kisses