Comprehensive schools have been accused of grade inflation after a study revealed that Gymnasium senior students of average mathematical ability found themselves at the very bottom of their class and had an average grade of "Five", which means "Failed". Gesamtschule senior students of average mathematical ability found themselves in the upper half of their class and had an average grade of "Three Plus". When a central Abitur examination was established in the State of North Rhine-Westphalia, it was revealed that Gesamtschule students did worse than could be predicted by their grades or class rank. Barbara Sommer (Christian Democratic Union), Education Minister of North Rhine-Westphalia, commented that: Looking at the performance gap between comprehensives and the Gymnasium [at the Abitur central examination] [...] it is difficult to understand why the Social Democratic Party of Germany wants to do away with the Gymnasium. [...] The comprehensives do not help students achieve [...] I am sick and tired of the comprehensive schools blaming their problems on the social class origins of their students. What kind of attitude is this to blame their own students? She also called the Abitur awarded by the Gymnasium the true Abitur and the Abitur awarded by the Gesamtschule "Abitur light". As a reaction, Sigrid Beer (Alliance '90/The Greens) stated that comprehensives were structurally discriminated against by the government, which favoured the Gymnasiums. She also said that many of the students awarded the Abitur by the comprehensives came from "underprivileged groups" and sneering at their performance was a "piece of impudence".

Answer this question, if possible (if impossible, reply "unanswerable"): Which party does Sigrid Beer belong to?
Alliance '90/The Greens