Final answer:
The 1920s in the United States was marked by the development of a consumer advertising industry, which played a significant role in shaping the modern consumer culture of the time.
Step-by-step explanation:
During the 1920 in the United States, the development of a consumer advertising industry was significant and transformative. This era, known as the Roaring Twenties, saw the birth of modern consumer culture, partly due to the rise in mass production and technological advancements.
The other options listed, such as the creation of social welfare programs, rapid expansion of minority participation in politics, and strong legal rights for labor unions, were not characteristic changes of the 1920s. The advertising industry employed new marketing strategies to promote consumer goods, which differed dramatically from previous methods. Advertisers sought to persuade a growing middle-class audience, which was experiencing newfound disposable income, to embrace the consumer lifestyle, boosting sales in various sectors, including automobiles, fashion, and household goods.