Explanation
Correct answer: B.
Choice B is the best answer. The convention being tested is the use of punctuation around noun phrases. No punctuation is needed because the coordinated noun phrase "Thomas Hart Benton and Jackson Pollock" is a restrictive appositive, meaning that it provides essential identifying information about the noun phrase before it, "the renowned twentieth-century US artists."
Why the other choices are wrong
Choice A
Choice A is incorrect because no punctuation is needed between the noun phrase "the renowned twentieth-century US artists" and the restrictive appositive "Thomas Hart Benton and Jackson Pollock." Additionally, no punctuation is needed between the sentence’s subject ("paintings by the renowned twentieth-century US artists Thomas Hart Benton and Jackson Pollock") and the main verb ("were featured").
Choice C
Choice C is incorrect because no punctuation is needed between the coordinated elements "Thomas Hart Benton" and "Jackson Pollock." Additionally, no punctuation is needed between the sentence’s subject ("paintings by the renowned twentieth-century US artists Thomas Hart Benton and Jackson Pollock") and the main verb ("were featured").
Choice D
Choice D is incorrect because no punctuation is needed between the noun phrase "the renowned twentieth-century US artists" and the restrictive appositive "Thomas Hart Benton and Jackson Pollock."