The correct answer is B. Replace the comma after persists with a colon.
Step-by-step explanation
A colon (:) is a punctuation mark represented by one period above another. Its main function is to stop the speech to draw the reader's attention to what is next in the text. Its most common uses are in the explanatory enumeration and the introduction of quotes or verbatim words.
According to the above, it can be inferred that the correct answer is B because in the sentence "According to Stonehill, a primitive standard of attractiveness persists, "Some researchers have ..." " the author is adding a quote and it would be appropriate to replace the comma after persists with a colon.