If you’re referring to the order in which they occurred, it’s 2 then 1 then 3 then 4
Answer:In 1947, Salk took a position at University of Pittsburgh, where he began conducting research on polio, also known as infantile paralysis. By 1951, Salk had determined that there were three distinct types of polio viruses and was able to develop a "killed virus" vaccine for the disease.
Explanation:
D) immigrants tried to blend into American culture as quickly as possible
