Answer:
The correct answer is amables.
Step-by-step explanation:
An adjective is that word that accompanies the noun and expresses a quality of that noun, qualifies it, or shows a concrete or abstract property.
There are several types of adjectives, qualifiers, demonstratives, numerals, possessives, etc.
In this case, you should pay attention that the adjective must coincide with the subject to which it is referring, in this case "Sus hermanas". As we can see, it is more than one person, so the adjective we are looking for must be in the plural form.
This shows us that the correct answer is amables.