The correct answer is B) Quota system
Literacy tests were used to prevent individuals from voting, not entering the United States.
Health exams and criminal records were pieces of evidence gathered at Ellis and Angel Island to learn more about immigrants. However, these measures were not implemented by Congress. Rather, they were up to the workers of these individual immigration processing centers.
The quota system was the only one used by Congress. An example of this would be the Immigration Act of 1924, which limited the number of immigrants based on which country they came from.
