Most workers for the central pacific railroad were
irish
french
german
chinese

The correct answer is: "Chinese".

The Central Pacific Railroad connected California and Utah since the 1860s decade. It was constructed as the Western branch of the "First Transcontinental Railroad" located in North America.

Chinese immigrants were a crucial labor source during the construction of the railroad. More and more Chinese men continued arriving and were hired even tough the working conditions were extremely harsh and they received less compensation that their white counterparts.  

interdependence is when all participating groups and individuals depend on each other. if you depend on one anothers goods, you end up trading in order to get the items you're looking for. (for ex: if i have food and you have water, we trade in order to depend on each other to live)

answer; the period of time known as the middle ages;