Right answer:
c. interesantes
A Lili, los discos compactos le parecen interesantes
interesantes is an adjective that means interesting. An adjective is a word that gives us more information about a noun or pronoun. In this case, interesantes is a descriptive adjective. Those types of adjectives are used to describe some quality of a noun like size, color, or shape of a person, an animal, a thing, or a place. Adjectives must agree with the noun or pronoun they describe in both number and gender. The adjective interesantes doesn't have gender but is the plural form of the adjective interesante because the noun of this sentence is plural (discos compactos).