Answer:
gordas
Step-by-step explanation:
Las gatas no son delgadas , son gordas.
The subject and predicate must match in number and person.
The adjective (gordas) must match in gender and number with the noun (gatas) it modifies.
In english when you say ¨cat¨, you don´t have a gender. In spainsh ¨gato¨ is a male cat and ¨gata¨ is a female cat.
Translation:
Cats aren't thin, they're fat.