Which sentence shows the correct way to capitalize the underlined titles?

a. my grandparents call my great-grandfather "the general" because he fought in the civil war.

b. my grandparents call my great-grandfather "the general" because he fought in the civil war.

c. my grandparents call my great-grandfather "the general" because he fought in the civil war.

d. my grandparents call my great-grandfather "the general" because he fought in the civil war?