Question

Write the correct direct object pronoun to replace the words in italics.

Answer 1

Nous les ecoutons.
Nos soeurs, meaning our sisters, are third person plural, meaning that we also need a plural pronoun here, which is les for both males and females in French. These are all personal pronouns for direct objects in French: me, te, le/la, nous, vous, les. 

Answer 2

Hi,
Write the correct direct object pronoun to replace the words in italics.
Nous _____ ecoutons. (nos soeurs)
Nous les écoutons.