B is going to be your answer
Answer:
1) sus libros son viejos
2) tu escuela está cerca
3) nuestra hermana no es delgada
According to the option provided the answer would be "¡ Ella está guapa en su traje de novia!" This would mean that she is pretty in her wedding dress.
if we pay attention to the verb form, it might be said that it agrees in gender and number with the subject pronoun "ella". It is 3rd person singular and feminine. <span />