It is because the price of products dropped in the gilded age and that is because they made the transport of stuff and services way cheaper that lowered the cost to make them and therefor the price
Your answer is <span>B.Railroads provided cheap and fast transportation for both raw materials and products.</span>
According to the sentence we would say that this kind of effect is normally related to the race crossover and it refers that the African American centenarians live longer than do European American Centenarias.