When Hijra started?

A. 12th of Rabi-ul-Awwal of 13th year of Nabawat

B. 12th of Rabi-ul-Awwal of 12th year of Nabawat

C. 12th Rabi-ul-Awwal of 14th year of Nabawat

D. 12th Rabi-ul-Awwal of 10th year of Nabawat