The correct option is D c
Let’s examine the sentence: “The Chairman's comments on future policy introduced a jarring note for the proceedings.” The sentence implies that the ‘jarring note’ has been introduced while the ‘proceedings’ are going on. Hence, instead of ‘for,’ ‘in’ should be used. So, ‘for the proceedings’ in the sentence should be replaced by ‘in the proceedings.’ So, the error is in Part C of the sentence. Hence, Option C is the correct answer.