Hey there!
The answer to your question is the first option: "Born in 1940, Olympian Wilma Rudolph's life would have been much different had the polio vaccine already been discovered."
This is because this topic sentence is a sentence that sounds like it starts a new paragraph, unlike the other options, they are sentences that belong in the middle/end of a paragraph.
Final answer:
First option.
Hope this helps you.
Have a great day!