Final answer:
The Chinese Exclusion Act of 1882 was the only legislative act to place a ban on immigrants from a specific region, targeting Chinese laborers specifically due to their race or ethnicity and was finally repealed in the 1940s with certain quotas.
Step-by-step explanation:
The only federal legislative act to ban immigrants based on a specific region is a) The Chinese Exclusion Act.
The Chinese Exclusion Act of 1882 was a significant piece of legislation that prohibited the immigration of Chinese laborers to the United States. It was the first law in U.S. history to prevent a group of immigrants explicitly due to their race or ethnicity. The act targeted Chinese workers who were seen as a threat to the employment market, particularly in the West Coast. Although the law prevented the migration of Chinese laborers, it allowed certain groups of Chinese individuals, such as wealthy investors, to migrate. This act contributed to an environment of intolerance and was a clear example of nativist sentiment that affected Asian immigrants in the United States.
It wasn't until WWII, due to America's alliance with China, that sentiments began to shift, and the act was finally repealed in the 1940s. However, the repeal came with a quota, which only permitted a small number of Chinese immigrants each year.