Who was the founder and first caliph of the Abbasid Caliphate?

(A) Abbas ibn Abd al-Muttalib (R.A)
(B) Mu’awiya ibn Abi Sufyan (R.A)
(C) Ali ibn Abi Talib (R.A)
(D) Hasan ibn Ali (R.A)

The answer is: (A) Abbas ibn Abd al-Muttalib (R.A)
Abbas ibn Abd al-Muttalib (R.A) was a paternal uncle of Prophet Muhammad (PBUH). He was the founder and first caliph of the Abbasid Caliphate.