The Abbasids took over power from Ummaiyyads in the year :

Question

Accepted Answer

The correct option is 3:
The Abbasid Caliphate overthrew the Umayyad Caliphate in 750 A.D. This transfer of power, known as the Abbasid Revolution, fundamentally changed the nature and focus of the Islamic Empire. The Umayyads had ruled since 661 A.D. and were seen by many as favoring Arab Muslims over non-Arab converts (known as Mawali), and ruling as secular kings rather than spiritual leaders. The Abbasids, who were descended from Muhammad’s uncle, al-Abbas, successfully led a revolt drawing support from non-Arab Muslims, particularly in Khurasan. The decisive Battle of the Zab in 750 A.D. led to the defeat of the last Umayyad Caliph, Marwan II, and the establishment of the Abbasid dynasty, which shifted the capital eastward from Damascus to Baghdad and ushered in the Islamic Golden Age.

The incorrect option is 1:
661 A.D. is incorrect because this year marks the beginning of the Umayyad Caliphate itself. After the death of Ali, the fourth Rashidun Caliph, Mu'awiya established the Umayyad dynasty, starting their nearly century-long rule.

The incorrect option is 2:
656 A.D. is incorrect as this date is associated with a period of turmoil leading up to the end of the Rashidun Caliphate. Specifically, the third Caliph Uthman was assassinated in 656 A.D., an event followed by the reign of Ali and the First Fitna (civil war).

The incorrect option is 4:
644 A.D. is incorrect because this date precedes the Umayyad rule and is associated with the assassination of the second Caliph, Umar. This event occurred during the period of the Rashidun Caliphate, well before the Umayyads took power and decades before the Abbasids overthrew them.