To answer this question, we need to identify the part of the sentence that contains an error.
The correct form of the sentence should be: "If I were you, I would not have committed this blunder."
Option A) a - This option is correct because the phrase "If I was you" should be corrected to "If I were you." In conditional sentences, the subjunctive mood is used to express hypothetical or contrary-to-fact situations. In this case, the correct form of the verb "to be" is "were" instead of "was."
Option B) b - This option is incorrect. The verb "have" is correctly used in the sentence.
Option C) c - This option is incorrect. The phrase "committed this blunder" is correctly used in the sentence.
Option D) d - This option is incorrect. The sentence contains an error, so "No error" is not the correct answer.
Therefore, the correct answer is Option A) a because it contains the error in the sentence.