The correct option is B (b)
Let’s examine the sentence: “It is high time we carried a halt to the existing corrupt practices followed in the educational sphere.” The phrasal verb is “put a halt” and not “carried a halt.” So, to correct the sentence, “carried” should be replaced by “put” in it. Hence, the correct version of the sentence would be, “It is high time we put a halt to the existing corrupt practices followed in the educational sphere.” So, the error is in Part b of the sentence. Hence, Option B is the correct answer.