Which one of the following best describes the effect industrial unionism has had on the wages of Black workers relative to those of White workers, as that effect is presented in the passage? A. Prior to 1947, industrial unionism had little effect on the wages of Black workers relative to those of White workers: since 1947, it has had a slight positive effect. B. Prior to 1947, industrial unionism had a strong positive effect on the wages of Black workers relative to those of White workers: since 1947, it has had little effect. C. Prior to 1947, industrial unionism had a negative effect on the wages of Black workers relative to those of White workers: since 1947, it has had a significant positive effect. D. Industrial unionism has contributed moderately to an increase in the wage differential between Black workers and White workers. E. Industrial unionism has contributed strongly to a 3 percent decrease in the wage differential between Black workers and White workers.