The answer is for sure D.
A) The author chooses to concede the point and offers no rebuttal. This is wrong because the author says, "Students without phones are actually at a disadvantage in the classroom."
B) The author offers an opinion discounting the counterclaim. This is wrong because the author includes, "A 2013 Educator Insider poll reveals that 67% of high school instructors now encourage students to use phones in the classroom setting." This is a poll with facts, not just an opinion.
C) The author ignores the counterclaim and avoids responding. This is definitely wrong because the entire paragraph is a response.
D) The author supplies a rebuttal that quotes more current research. This is the only logical solution and is accurate based on the paragraph given.