Help me pls thank you

Does anyone know what my spanish teacher means by this? i need to use plural forms of the verb ser. and she asked me to use a couple of adjectives to describe the boys collectively and then the girls collectively?

Completa la oración con la voz pasiva con se. used cars for sale. carros usados. (there are no option choices, write the answer in the passive tense, don't use google translate)

Choose the most logical choice to complete each sentence. los animales al río