Final answer:
Julia is the other sister of Augustus and is married to Marc Antony.
Step-by-step explanation:
Julia, the woman who accompanies Augustus when he visits Terentia in the Domus Vestalis, is **Option C: the other sister of Augustus, married to Marc Antony**. This makes her the sister-in-law of Augustus. She was the daughter of Augustus's second wife, Scribonia, and her marriage to Marc Antony was a strategic union aimed at solidifying the political alliance between the two men.
Learn more about Julia's relationship to Augustus and Marc Antony