Task: Question Answering
Input (English): Sentence: In 1836, at a party hosted by Marie d'Agoult, Chopin met the French author George Sand (born [Amantine] Aurore [Lucile] Dupin). Short (under five feet, or 152 cm), dark, big-eyed and a cigar smoker, she initially repelled Chopin, who remarked, "What an unattractive person la Sand is. Is she really a woman?" However, by early 1837 Maria Wodzińska's mother had made it clear to Chopin in correspondence that a marriage with her daughter was unlikely to proceed. It is thought that she was influenced by his poor health and possibly also by rumours about his associations with women such as d'Agoult and Sand. Chopin finally placed the letters from Maria and her mother in a package on which he wrote, in Polish, "My tragedy". Sand, in a letter to Grzymała of June 1838, admitted strong feelings for the composer and debated whether to abandon a current affair in order to begin a relationship with Chopin; she asked Grzymała to assess Chopin's relationship with Maria Wodzińska, without realising that the affair, at least from Maria's side, was over. 
Question: Who was the host of the gathering where Frédéric was introduced to George Sand?
Output (English): Marie d'Agoult