Final answer:
The novel 'The Private Life of Helen of Troy' is set in Sparta after Helen's return. Sparta was a prominent Greek city-state known for its military prowess and played a significant role in ancient Greek history, particularly in conflicts like the Peloponnesian War and the Battle of Thermopylae.
Step-by-step explanation:
The bestseller The Private Life of Helen of Troy takes place after Helen returns to the Greek city-state of Sparta (A). Helen of Troy is a figure from Greek mythology who was considered one of the main reasons for the Trojan War. Following the war, she returned to her husband, King Menelaus, in Sparta. Historical context around Sparta includes its critical role in various conflicts such as the Battle of Thermopylae and the Peloponnesian War. Significantly, the Battle of Leuctra was a major defeat for Sparta against Thebes, leading to the decline of its power.