Answer the following question: Information:  - Troy ("Troia" and , "Ilion", or , "Ilios"; and ; Hittite: "Wilusha" or "Truwisha") was a city situated in the far northwest of the region known in late Classical antiquity as Asia Minor, now known as Anatolia in modern Turkey, near (just south of) the southwest mouth of the Dardanelles strait and northwest of Mount Ida. The present-day location is known as Hisarlik. It was the setting of the Trojan War described in the Greek Epic Cycle, in particular in the "Iliad", one of the two epic poems attributed to Homer. Metrical evidence from the "Iliad" and the "Odyssey" suggests that the name ("Ilion") formerly began with a digamma: ("Wilion"); this is also supported by the Hittite name for what is thought to be the same city, Wilusa.  - In Greek mythology, Hector ("Hektr") was a Trojan prince and the greatest fighter for Troy in the Trojan War. As the first-born son of King Priam and Queen Hecuba, who was a descendant of Dardanus and Tros, the founder of Troy, he was a prince of the royal house and the heir apparent to his father's throne. He was married to Andromache, with whom he had an infant son, Scamandrius (whom the people of Troy called Astyanax). He acted as leader of the Trojans and their allies in the defense of Troy, "killing 31,000 Greek fighters", offers Hyginus. During the European Middle Ages, Hector figures as one of the Nine Worthies noted by Jacques de Longuyon, known not only for his courage but also for his noble and courtly nature. Indeed, Homer places Hector as peace-loving, thoughtful as well as bold, a good son, husband and father, and without darker motives. James Redfield writes of Hector as a "martyr to loyalties, a witness to the things of this world, a hero ready to die for the precious imperfections of ordinary life."  - The Dardanelles, also known in Classical Antiquity as the Hellespont ("Hellespontos", literally "Sea of Helle"), is a narrow, natural strait and internationally-significant waterway in northwestern Turkey that forms part of the continental boundary between Europe and Asia, and separates Asian Turkey from European Turkey. One of the world's narrowest straits used for international navigation, the Dardanelles connects the Sea of Marmara with the Aegean and Mediterranean Seas, while also allowing passage to the Black Sea by extension via the Bosphorus.  - In Greek mythology , Polyxena ( / plksn / ; Greek :  ) was the youngest daughter of King Priam of Troy and his queen , Hecuba .  - Cassandra (, also ), also known as Alexandra or Kassandra, was a daughter of King Priam and of Queen Hecuba of Troy. In modern usage her name is employed as a rhetorical device to indicate someone whose accurate prophecies are not believed by those around them.  - Hecuba (also "Hecabe", "Hécube"; "Hekáb") was a queen in Greek mythology, the wife of King Priam of Troy during the Trojan War, with whom she had 19 children. These children included several major characters of Homer's "Iliad" such as the warriors Hector and Paris and the prophetess Cassandra.    Given the information above, choose from the list below the object entity that exhibits the relation 'sister' with the subject 'polyxena'.  Choices: - andromache  - helle  - kassandra
Answer:
kassandra