Final answer:
Asian immigrants, who arrived during the Gold Rush, often found jobs helping to build the transcontinental railroad as gold became harder to find.
Step-by-step explanation:
After the Gold Rush drew many people to the West in 1849, Asian immigrants, mainly from China, came to the Pacific region in search of opportunities. As it became more challenging to find gold, many of these immigrants found employment in constructing the transcontinental railroad. The Central Pacific Railroad hired thousands of Chinese migrant workers to lay railway tracks across challenging terrain, such as the Sierra Nevada mountains.
This workforce played a pivotal role in the successful completion of the transcontinental railroad, a remarkable engineering feat that connected the east and west coasts of the United States.
The option that answers the student's question is: a) Railroad.