Final answer:
The sentence needs a comma after 'age of 12' before the conjunction 'but' to properly separate the two independent clauses.
Step-by-step explanation:
The text you've provided should include a comma to separate the two clauses for correct punctuation. The revised sentence with the proper punctuation is as follows:
Wilma Rudolph battled polio until the age of 12, but went on to become the first American woman to win three Olympic gold medals.
Adding this comma clarifies the sentence structure and ensures each independent clause is properly punctuated. Commas before conjunctions like 'but' help to coordinate two independent clauses within a single sentence.
The correct punctuation for the given sentence is a semicolon. The sentence should be written as:
Wilma Rudolph battled polio until the age of 12; but went on to become the first American woman to win three Olympic gold medals.
A semicolon is used to join two independent clauses that are closely related in meaning. In this case, the two clauses are 'Wilma Rudolph battled polio until the age of 12' and 'went on to become the first American woman to win three Olympic gold medals.'