Which wife of the Prophet (PBUH) was titled Umm-ul-Momineen first?

1. Hazrat Khadijah (RA)
2. Hazrat Aisha (RA)
3. Hazrat Hafsa (RA)
4. Hazrat Saudah (RA)

Hazrat Khadijah (RA) was the first wife of the Prophet (PBUH) and the first to be honored with the title “Mother of the Believers.”