听力原文： Up to about 1915, movies were short and programs were made up of several works. Then, D. U. Griffith and others began to make longer films which provided the same powerful emotional appeal as did melodrama and presented spectacles far beyond what the theater could after. Consequently, after world war I increasing numbers of spectators deserted the theater for the movies. This trend was accelerated in the late 1920's as a result of two new elements. In 1927 sound was added to the previously silent film, and thus one of the theaters principal claims to superiority vanished. In 1929 a serious economic depression began, Since audiences could go to the movies for a fraction of What it cost to see a play, theater going became a luxury Which few could afford, especially as the depression deepened. By the end of world war II , the American theater had been reduced to about thirty theaters in New York city and a small number of touring companies originating there. Why did movies do better than theater?