The most accurate summary based on cause and effect for the expansion of Muslim Empires is:
Cause: leadership changes and military conquest
Effect: The Umayyad Caliphate expanded to Syria and centralized Islamic power.
Cause: political revolts
Effect: The Abbasid caliphate expanded to Iraq and developed socially and culturally.
This summary correctly attributes specific causes (leadership changes, military conquest, and political revolts) to their respective effects in the context of the Umayyad and Abbasid Caliphates, highlighting their expansions and societal developments.