1. two men gave big strides in science during the early twentieth century: norman borlaug and jonas salk. pick one of these two men and briefly describe their contribution to society.

One man who helped science to make great strides in the twentieth century was Jonas Salk who invented the Salk vaccine for polio prevention. It was the first safe and effective vaccine for polio. Also, he invented an influenza vaccine. He obtained a PhD in medicine and went into research rather than as a medical practicioner. He lived from 1914-1995.

Yes, reasons why is sectionalism compromise of 1850 and secession i hope this