Explanation
Correct answer: D.
Choice D is the best answer. The convention being tested is the punctuation of a supplementary element within a sentence. The dash after “Ecuador” and the closing parenthesis pairs with the dash after “territories” to separate the supplementary element (“New…Ecuador”) from the rest of the sentence. The supplementary element specifies the three South American territories that Simón Bolívar liberated, and the pair of dashes indicates that this element could be removed without affecting the grammatical coherence of the sentence.
Why the other choices are wrong
Choice A
Choice A is incorrect because it fails to use appropriate punctuation to separate the supplementary element from the rest of the sentence. Furthermore, punctuation isn’t needed between “Ecuador” and the closing parenthesis.
Choice B
Choice B is incorrect because it fails to use appropriate punctuation to separate the supplementary element from the rest of the sentence.
Choice C
Choice C is incorrect because a comma can’t be paired with a dash to separate the supplementary element from the rest of the sentence.