You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Russian_language

Context:
In the 20th century, Russian was mandatorily taught in the schools of the members of the old Warsaw Pact and in other countries that used to be satellites of the USSR. In particular, these countries include Poland, Bulgaria, the Czech Republic, Slovakia, Hungary, Albania, former East Germany and Cuba. However, younger generations are usually not fluent in it, because Russian is no longer mandatory in the school system. According to the Eurobarometer 2005 survey, though, fluency in Russian remains fairly high (20–40%) in some countries, in particular those where the people speak a Slavic language and thereby have an edge in learning Russian (namely, Poland, Czech Republic, Slovakia, and Bulgaria).

Question:
Where was Russian schooling mandatory in the 20th century?

Poland, Bulgaria, the Czech Republic, Slovakia, Hungary, Albania, former East Germany and Cuba