The correct answer is actually A. Toe dancing was developed in the early nineteenth century, but it was not widely used until the 1830s.
A comma splice incorrectly connects two independent clauses - where there should be a conjunction, a comma is incorrectly placed, like in the example above.
B is incorrect because the only thing that changed was that the comma was deleted - it didn't actually fix anything; C is incorrect because the subject is missing after yet - it should be: ...yet IT was not widely used... D is incorrect because there should be a semicolon (;) in front of however and not a comma.