Correct me guys, if I am wrong. I think the answer should be B and the OA - D is wrong.
To those of you, who are still confused regarding the use of that vs. which,
Consider the following example
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That vs which: restrictive and nonrestrictive clauses. Restrictive clauses are essential to the meaning of a sentence, while unrestrictive clauses are parenthetical. Unrestrictive clauses are always set off with commas, and restrictive clauses are never set off with commas. Which is appropriate for unrestrictive clauses, and that is appropriate for restrictive clauses.
Example of an unrestrictive clause: "The story, which appeared on the second page, was compelling."
Or, written to include a restrictive clause: "The story that appeared on the second page was compelling."
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As a comma precedes "that" in choice D, choice D is out. Besides, the use of "is" is wrong. As the that refers to "pharmaceutical advertisements", the word "are" should follow.
IMHO, the answer should be B.
PS - if the answer is not B, then my grammar fundas are in for a major overhaul. (fingers crossed)