Final answer:
The usage of the auxiliary verbs 'avoir' and 'être' in French sentences.
Explanation:
Avoir and être are the two auxiliary verbs used in French to form compound tenses.
In Gisèle's e-mail, the correct auxiliary verbs to complete the sentences are:
- Je suis allée à Marseille - I went to Marseille
- On a quitté Paris - We left Paris
- On est arrivé chez mon cousin Régis - We arrived at my cousin Régis's
- On a pris le métro tous les jours - We took the metro every day
- On a visité les gorges du Verdon - We visited the Verdon Gorges
Learn more about Auxiliary verbs in French here:
https://brainly.com/question/44135546