Final answer:
The Battle of Actium, a naval engagement in 31 BCE, was fought at the Ionian Sea near Actium in Greece, between the forces of Octavian and the joint forces of Marc Antony and Cleopatra. It resulted in Octavian's victory and led to the Roman Empire's beginning.
Step-by-step explanation:
The Battle of Actium was fought on the Ionian Sea near the promontory of Actium in northwestern Greece on September 2, 31 BCE. This naval confrontation was the decisive engagement in the final war of the Roman Republic between the forces of Octavian and those of Marc Antony, allied with Cleopatra VII of Egypt. The victory at Actium gave Octavian control over the Roman world and led to the establishment of the Roman Empire, with Octavian taking the title Augustus.
The climax of the conflict, the Battle of Actium, was not at Pharsalus but at Actium, making the correct answer to the multiple-choice question (b) Actium. Following their defeat, Antony and Cleopatra fled to Egypt where they ultimately took their own lives. This series of events marked the end of the Ptolemaic Kingdom and the beginning of Roman hegemony in Egypt.