Correct Answer and Explanation:
The correct answer is D) shallowness, an example of.
Explanation
Original (A): The original version creates a run-on sentence (specifically, a comma splice if we assume the first period is meant to be a comma, or two awkwardly short, redundant sentences as written). The second sentence starts an explanation that is better integrated into the first.
Choice B and C: Both misuse the semicolon (;). A semicolon must separate two independent clauses (two complete sentences). The phrase "an example of the lowest common denominator..." is a dependent phrase (an appositive) and cannot follow a semicolon without forming a grammatical error.
Choice D (Correct): This option uses a comma followed by an appositive phrase ("an example of...") to efficiently and grammatically rename or describe the noun that precedes it ("shallowness"). It eliminates the redundant and wordy phrasing ("It is a very simplistic joke, and they find it to be") for a more concise and rhetorically effective sentence, which is a key focus of the SAT.