Final answer:
The plural form of the sentence should be 'Ellas son inteligentes y cómicas'.
Step-by-step explanation:
The correct plural form of the sentence "Ella es inteligente y cómica" is option b. Ellas son inteligentes y cómicas. When talking about a group of females in Spanish, the plural subject pronoun "ellas" is used, along with the corresponding plural form of any adjectives used to describe them. In this case, the adjective forms are "inteligentes" (intelligent) and "cómicas" (funny).
Learn more about Plural forms in Spanish