Central America is the subject of the sentence.
Answer:
C)It causes conflict between him and his parents. Explanation: The narrator spent most of his time listening to music and joined musical classes and bands. Due to this his focus from studies vanished and grades were effected badly.
Monitor is a concrete noun.
A concrete noun is something material. Basically, just remember that if you can touch it, it's concrete!
Abstract nouns are usually feelings, such as anger, happiness, sadness. If you can't touch it, it's abstract!
If you have any questions about how to differentiate concrete and abstract nouns, just ask!
Good luck :))