According to paragraph 6, which of the following accounts for the delay in the conversion to sound films in Europe? A. European producers often lacked knowledge about the necessary equipment for the transition to sound films. B. Smaller European producers were often unable to afford to add sound to their films. C. It was often difficult to wire older cinemas in the major cities to play sound films. D. Smaller European producers believed that silent films with music accompaniment were aesthetically superior to sound films.