Answer:
Step-by-step explanation:
La fille parle à ses sœurs. → La fille leur parle. = to who is she talking ? to them = complement of the indirect object (COI, hope it's the good translation) : leur
Vous retrouvez vos amis sous le préau. → Vous les retrouvez sous le préau. = you find again who ? Them = complement of the direct object (COD) : les
La fille écoute son père. → La fille l'écoute. = who does she listen (to) ? (to) him = complement of the direct object (COD in french) and the verb starts with a vowel so we take out the vowel : le → l'
Sally obéit à sa soeur. → Sally lui obéit. = who does she obey to ? to her = complement of the indirect object : lui
J'attends quelqu'un. → Je l'attends. = who am I waiting (for) ? (for) someone but the verb starts with a vowel so we take out the vowel = le / la → l'