Intense pressure and heat in the Earth’s mantle transform carbon atoms, altering their lattice structure. Occasionally, these forces create ______ a rare form of diamond with a hexagonal crystal structure found in meteorites.
Which choice completes the text so that it conforms to the conventions of Standard English?
lonsdaleite. Lonsdaleite being
lonsdaleite;
lonsdaleite,
lonsdaleite
Correct Answer: C
Choice C is the best answer. The phrase "a rare form of diamond..." functions as an appositive that renames and provides additional information about the noun "lonsdaleite." Standard English conventions require a comma to separate this nonrestrictive element from the noun it modifies.
Choice A is incorrect because it creates a redundant and fragmented new sentence structure. Choice B is incorrect because a semicolon is used to join two independent clauses, but the phrase following "lonsdaleite" is a dependent appositive phrase, not a complete sentence. Choice D is incorrect because it fails to punctuate the nonrestrictive appositive, resulting in a run-on structure.