Most immigrants who passed through ellis island were european, but most who passed through angel island were asian. what is the most likely reason for this?

First, we will talk about the immigrants from Europe. Europe is located across the US with the Atlantic Ocean between them. Many Europeans that leave for the US travel to the west coast before boarding a ship that leads them to Ellis Island. Ellis Island is located in the upper part of New York Bay, and was one of the most busiest immigration inspection station. 

Those from Asia, however, travel through the Pacific Ocean, and end up at Angel Island, located in the San Francisco Bay. San Francisco is located in California, in the west part of the US, and is the closest, most direct route from China to there, which meant that Asian immigrants landed at Angel Island instead of Ellis Island. 

hope this helps