A、In 1800. B、In 1851. C、In 1939. D、In 1950. B

The Universal Expo, also known as World’s Fair, is one of the three largest events in the world in terms of economic and cultural impact. However, compared with the other two great events, the modern Olympic Games and the World Cup, the Expo has the longest history. In 1851, the first Expo was held in London, under the title "Great Exhibition of the Works of Industry of All Nations".
    At the Expo, participating countries will set up their national pavilions in distinctive architectural styles, with a view to attracting business people and tourists all over the world. The cost for building such a pavilion could amount to millions of dollars. But it is often far outweighed by benefits and potential revenues thus generated. Usually an expo will last between three and six months.
    The character of world expositions has developed through history. Three stages are identified, namely, the eras of industrialization, of cultural exchange, and of nation branding. The first era covered, roughly, the period from 1800 to 1950. In these days, world expositions were especially focused on trade and famous for the display of scientific and technological advancements. The second era started with the 1939 New York World’s Fair. From then on, World’s Fairs became more strongly based on a specific theme of cultural significance. Technology and inventions remained important, but no longer as the principal subjects. The defining elements of the expos were cross-cultural communications and exchanges. Finally, in the early 1990s, countries started to use World Expositions more widely and strongly as a platform to improve their national images. A study shows that improving national image was the primary participation goal for 73% of the countries at Expo 2000. Today’s world expositions embody elements of all three eras. They present new inventions, facilitate cultural exchange, and are used for city, region and nation branding.
Question No. 15 When was the first World Expo held?
Question No. 16 According to the talk, why do participating countries build their national pavilions at the Expo?
Question No. 17 At Expo 2000, what was the primary goal for the majority of participating countries?
Question No. 18 Which of the following is NOT an element represented in the Expo?