Answer:
1. Lupe, Rosa y Tomás son (bueno) amigos. The form of the adjective 'bueno' (good) is incorrect
2. Ignacio es (alto) y (guapo). The forms of the adjectives 'alto' (tall) and 'guapo' (handsome) are correct.
3. Laura y Virginia son (bajo) y (delgado). The forms of the adjectives 'bajo' (short) and 'delgado' (thin) are incorrect
4. Pedro y Vanessa son (moreno), pero Diana es (pelirrojo). The forms of the adjectives 'moreno' (having black skin) and 'pelirrojo' (red-haired) are incorrect
5. Nosotras somos (inteligente) y (trabajador). The form of the adjectives 'inteligente' (intelligent) and 'trabajador' (hard-working) are incorrect
6. Esos (Those) chicos son (simpático), pero son (tonto). The forms of the adjectives 'simpático' (nice) and 'tonto' (silly) are incorrect.
Explanation:
1-
In the first sentence, 'Lupe, Rosa y Tomás son (bueno) amigos.', the adjective (adjective is a feature of a person or object) 'bueno' (good) needs to take a final -s (buenos) to pluralize for it is a rule from Spanish grammar that adjectives take plural form when the subject (subject is the person who the sentence speaks about) is plural. In this case the subject is made up of three people (plural) together: 'Lupe, Rosa y Tomàs'
2-
This second sentence, 'Ignacio es (alto) y (guapo).' is correct for the subject is only one person (singular) and therefore the adjectives 'alto' (tall) and 'guapo' (handsome) are in the singular forms (in other words, without -s at the end)
3-
This third case, 'Laura y Virginia son (bajo) y (delgado).', is similar to the first one for we have a subject made up of two people (plural), 'Laura and Virginia' and thus the adjectives 'bajo' (short) and 'delgado' (thin) should have to pluralize (take a final -s to form the plural form): 'Laura y Virginia son (bajas) y (delgadas).'. On the other hand, as we are talking about two women, the adjectives need to take female reference as well (in Spanish, female reference is achieved by adding 'a' instead of 'o' to the end of adjectives. For example: bajo- refers to a short man; baja-refers to a short woman; delgado-thin man; delgada-thin woman)
4-
In this fourth case, 'Pedro y Vanessa son (moreno), pero Diana es (pelirrojo).', we are talking about two people together functioning as subject: 'Pedro y Vanessa'. As they are two (plural), the adjective 'moreno' (having black skin colour) needs to take plural form by adding a final -s: 'Pedro y Vanessa son morenos'.
In the second part of this sentence,'...pero Diana es pelirrojo.' we have to change the final vowel of the adjective from 'o' into 'a', so that it changes from referring to a man 'pelirrojo' (man with red hair) to a woman 'pelirroja' (woman with red hair)
5-
In this fifth case, 'Nosotras somos (inteligente) y (trabajador).', once again there is a plural subject 'Nosotras'. However, the adjectives 'inteligente' (intelligent) and 'trabajador' (hard-working) make reference to only one person (singular). In order to solve this problem, we have to add a final -s to the adjectives so that we get 'inteligentes' and 'trabajadoras'
6-
In this sixth case, 'Esos (Those) chicos son (simpático), pero son (tonto).', there is a plural subject 'Esos chicos' (Those boys). However, the adjectives 'simpàtico' (nice) and 'tonto' (silly) are in their singular forms when they should be in the plural forms (adding a final -s at the end): 'simpáticos' and 'tontos'
