Polyphenols are organic compounds __ among their many roles provide pigment that helps protect plants again ultraviolet radiation from sunlight Which choice completes the text so that it conforms to the conventions of Standard English? A. that- B. that; C. that, D. that;

The correct answer is C. that,<br /><br />The sentence should read: "Polyphenols are organic compounds that, among their many roles, provide pigment that helps protect plants against ultraviolet radiation from sunlight."<br /><br />The use of a comma after "that" is necessary to set off the non-restrictive clause "among their many roles," which provides additional information about the organic compounds but is not essential to the main meaning of the sentence.