Final answer:
The Atlantic Ocean marked the western tip of the Umayyad empire after their expansion into the Iberian Peninsula and across North Africa.
Step-by-step explanation:
The western tip of the Umayyad empire was marked by C) The Atlantic Ocean. After the Umayyad Caliphate's armies took Carthage, they continued their expansion across North Africa and into the Iberian Peninsula, culminating with the invasion of Spain in 711 CE. As the Umayyads continued to push northward, they reached as far as Narbonne, France, extending the empire's western border to the shores of the Atlantic Ocean. This geographical reach made the Umayyad Caliphate one of the largest empires in history at that time, spanning from the east in Iraq to the western edges of North Africa and into the Iberian Peninsula.