3. Which main idea is supported by this detail? Listening to music increases brain activity. A: Many students prefer playing a musical instrument rather than just listening to music.
B: It can be particularly helpful to listen to soft, classical music while completing homework.
C: Laughing, listening to music, and exercise all increase serotonin, also called the happy hormone.
D: Music has been known to have a direct impact on a person's mood and emotional state.

taking into account that a theme is the central topic a text treats and can be developed through a story, play, poem etc. the following are themes that can be further developed:  

my best friend jeffrey has many unusual interests. (the story could be about each of the unususal interests)

once a man gives his soul over to evil, he can never go back. (this could be a saying or a proverb)

the three sheepdogs lay around the yard all day. (it could be developed detailing how each of these sheepdogs lay around)

a priest's collar has an unusual effect upon people. (it could be developed detailing the different effect upon people)

innocence is a powerful force in a world full of corruption. (it could be developed detailing how is a world full of corruption)

king lear is a play shakespeare wrote later. (it is just a sentence and doesnt give any idea or topic to be discussed in details.

evil often wears the disguise of innocence. (this could be a saying or a proverb)

"a" because he is appealing to logic as oppose to appealing to the audience's emotions.