Question

what is the correct response to, \¿cómo está el muchacho?\
o el muchacho está nervioso.
o el muchacho está nerviosos.
o el muchacho está nerviosa.
o el muchacho está nerviosas.

Explanation:

In Spanish, "muchacho" (boy) is masculine - singular. Adjectives must agree in gender and number with the noun they modify. "Nervioso" is the masculine - singular form of the adjective "nervious", "nerviosa" is feminine - singular, "nerviosos" is masculine - plural and "nerviosas" is feminine - plural.

Answer:

El muchacho está nervioso.