In which sentence should the italicized word(s) be capitalized?

In which sentence should the italicized word(s) be capitalized? 
a. I went with my mom, dad, and two brothers to the state fair.
b. You have three choices of highlighter: red, green, or yellow.
c. Have you talked to aunt Judy today?
d. We went sailing on a lake about 100 miles from here.

(OpenStudy was used in the making of this answer)

1one sharp difficulty presented itself. in the intervening twenty-five years my name had become reasonably well known.2 this being so, my trip demanded that i leave my name and my identity at home.3 i had to go alone and i had to be self-contained, a kind of casual turtle carrying his house on his back.4 with all this in mind i wrote to the head office of a great corporation which manufactures trucks.