Respuesta :
Choice C is correct because it correctly uses "although" to combine the sentences, setting the subordinating conjunction off with a comma. Choice A incorrectly creates a sentence fragment, as "Although lower points may exist' is not a complete sentence. Choice B incorrectly uses a semicolon, as a semicolon should connect two complete sentences, and the phrase "although lower points may exist" is not a complete sentence. Choice D incorrectly places the comma after rather than before the subordinating conjunction.