Mario lit à ses enfants.
In this sentence, the word "ses enfants" is the indirect object, so it would be replaced by the COI. The appropriate COI for "ses enfants" would be "leur".
Nous donnons le journal aux enfants.
In this sentence, the word "aux enfants" is the indirect object, so it would be replaced by the COI. The appropriate COI for "aux enfants" would be "leur".
Tu achètes un cadeau pour Fatima.
In this sentence, the word "pour Fatima" is the indirect object, so it would be replaced by the COI. The appropriate COI for "pour Fatima" would be "lui".
Je pense à mes parents.
In this sentence, the word "à mes parents" is the indirect object, so it would be replaced by the COI. The appropriate COI for "à mes parents" would be "leur".
Il téléphone à son grand-père.
In this sentence, the word "à son grand-père" is the indirect object, so it would be replaced by the COI. The appropriate COI for "à son grand-père" would be "lui".
Now let's rewrite the sentences in negative form and translate them to English.
Leah donne les fleurs à Jamal.
Negative: Leah ne donne pas les fleurs à Jamal.
Translation: Leah does not give the flowers to Jamal.
La mère achète des vêtements pour les enfants.
Negative: La mère n'achète pas des vêtements pour les enfants.
Translation: The mother does not buy clothes for the children.
Tu as posé la question à ses étudiants.
Negative: Tu n'as pas posé la question à ses étudiants.
Translation: You did not ask the question to his/her students.
Il répond à Chantal le plus vite possible.
Negative: Il ne répond pas à Chantal le plus vite possible.
Translation: He does not answer Chantal as quickly as possible.
On a demandé au prof de vérifier la réponse.
Negative: On n'a pas demandé au prof de vérifier la réponse.
Translation: We did not ask the teacher to check the answer