Question: What is the date of birth of Kostja Zetkin's mother?
Sentence (from "Clara Zetkin"): Until 1917, she was active in the Social Democratic Party of Germany, then she joined the Independent Social Democratic Party of Germany (USPD) and its far-left wing, the Spartacist League; this later became the Communist Party of Germany (KPD), which she represented in the Reichstag during the Weimar Republic from 1920 to 1933.
Relevant evidence: No