Task: Question Generation
Input (English): Passage: The 19th century was dominated by the Hungarian struggle for independence and modernisation. The national insurrection against the Habsburgs began in the Hungarian capital Hungarian Revolution of 1848 and was defeated one and a half years later, with the help of the Russian Empire. 1867 was the year of Austro-Hungarian Compromise of 1867 that brought about the birth of Austria-Hungary. This made Budapest the twin capital of a dual monarchy. It was this compromise which opened the second great phase of development in the history of Budapest, lasting until World War I. In 1849 the Chain Bridge (Budapest) linking Buda with Pest was opened as the first permanent bridge across the Danube and in 1873 Buda and Pest were officially merged with the third part, Óbuda (Old Buda), thus creating the new metropolis of Budapest. The dynamic Pest grew into the countrys administrative, political, economic, trade and cultural hub. Ethnic Hungarians overtook Danube Swabians in the second half of the 19th century due to mass migration from the overpopulated rural Transdanubia and Great Hungarian Plain. Between 1851 and 1910 the proportion of Hungarians increased from 35.6% to 85.9%, Hungarian became the dominant language, and German was crowded out. The proportion of Jews peaked in 1900 with 23.6%. Due to the prosperity and the large Jewish community of the city at the start of the 20th century, Budapest was often called the "Jewish Mecca" or "Judapest". In 1918, Austria-Hungary lost the war and collapsed; Hungary declared itself an independent republic (Republic of Hungary). In 1920 the Treaty of Trianon partitioned the country, and as a result, Hungary lost over two-thirds of its territory, and about two-thirds of its inhabitants, including 3.3 million out of 15 million ethnic Hungarians.
Output (English): How many years after the Chain Bridge was opened did Buda and Pest merge?