Question

5) Instructor writes statements describing males or females or masculine or feminine things. ex. María es cómica. Paco es simpático. La carpeta es roja. El libro es rojo. Student underlines main areas of grammar (adjective agreement), and discusses the reason for the difference.

Tell me the main areas of adjective agreement and discuss the reason for the difference?

Answer 1

Simpatic-o, Roj-a, Roj-o these are the main areas of adjective agreement because they agree with their gender and number 
These are the type of adjective agreements 

Masculine Singular, Mascular Plural.
Feminine Singular, Feminine Plural.

The reason for the difference is because of gender or amount. Hope that helps :D