You are correct - the blank should be filled with an adjective and not a noun, therefore la cortes<span>ía is out.
To figure out which gender the adjective must take, take a look at the subject of the sentence. The subject here is u</span><span>n huésped; it contains the indefinite article un. The definite article that goes with un is el, which we know is masculine (feminine definite is la, and feminine indefinite is una).
Therefore, the adjective must be masculine - </span>respetuoso.
In a different scenario, where someone is saying this sentence to a female, they might say Es muy importante ser una huésped <span>respetuosa.</span>
Answer: Explanation:
Adjectives that don't change are because they're gender neutral:
Alegre: Alegre
Ordenada: Ordenado
• Inteligente: Inteligente
Moderna: Moderno
Hermosa: Hermoso
Pesada
: pesado
Fuerte: Fuerte
Aplicada
: Aplicado
Oscura: Oscuro
Limpia: Limpio