Researchers may assume that the Curiosity Rover was the first device to capture images of _________ actually, the Viking 1 lander sent back the first pictures from the surface in 1976.
Which choice completes the text so that it conforms to the conventions of Standard English?
Mars. But,
Mars, but
Mars. Actually
Mars; actually,
Correct Answer: D
Choice D is the best answer. The semicolon correctly separates two independent clauses, with "actually" functioning as a conjunctive adverb.
Choice A is incorrect because "But" is a conjunction and starting a sentence this way breaks the flow of the contrast being made. Choice B is incorrect because a comma cannot connect two independent clauses without a conjunction like "but" appearing after the comma, not before. Choice C is incorrect because "Actually" is not a conjunction, and a period breaks the close contrast.