Task: Question Generation
Input (English): The Monument in the City of London provides views of the surrounding area while commemorating the Great Fire of London, which originated nearby. Marble Arch and Wellington Arch, at the north and south ends of Park Lane respectively, have royal connections, as do the Albert Memorial and Royal Albert Hall in Kensington. Nelson's Column is a nationally recognised monument in Trafalgar Square, one of the focal points of central London. Older buildings are mainly brick built, most commonly the yellow London stock brick or a warm orange-red variety, often decorated with carvings and white plaster mouldings.
Output (English): What was the most common type of brick used to construct London's older buildings?