Answer:
B. Many Chinese people migrated there to work on the railroads, acquisition of the Mexican Cession area, and economic opportunities during the Gold Rush.
Step-by-step explanation:
The popularity of the Gold Rush spread all over the world, especially to China. By 1851, over 25,000 Chinese immigrants left home & moved to California, a land some called gam saan, or "gold mountain." Some immigrants eventually worked on the Transcontinental Railroad, which was finished in 1869.