15. Which of the following would be considered an $\omega$-3 fatty acid?
a. linoleic acid: 9,12-octadecadieneoic acid ($18:2\Delta^{9,12}$)
b. eicosapentaenoic acid: 5,8,11,14,17-eicosapentaenoic acid ($20:5\Delta^{5,8,11,14,17}$)
c. $\gamma$-linolenic acid: 6,9,12-octadecatrieneoic acid ($18:3\Delta^{6,9,12}$)
d. arachidonic acid: 5,8,11,14-eicosatetraenoic acid ($20:4\Delta^{5,8,11,14}$)
e. none of the above