I'm pretty sure that the answer is 'the Romans"
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:
Articles of Confederation, 1777–1781. The Articles of Confederation served as the written document that established the functions of the national government of the United States after it declared independence from Great Britain.