Final answer:
The correct response is "El muchacho es perezoso." The other options do not match the gender and number of the noun "muchacho."
Step-by-step explanation:
The correct response to the question, "¿Cómo es el muchacho?" is "El muchacho es perezoso." The word "perezoso" is the correct adjective to describe a male person as lazy. The other options, "perezosa" (feminine), "perezosas" (feminine plural), and "perezos" (incorrect form) do not match the gender and number of the noun "muchacho."
Learn more about Gender agreement in Spanish adjectives