The correct option is B b
Let’s examine the sentence: “The watch is a valuable present from my uncle and it costed him more than two thousand rupees.” The sentence uses “costed,” which is wrong as “cost” is used as it is in all the three forms of this verb. Hence, “cost” would be used here instead of “costed.” So, the error is in Part b of the sentence. Hence, option B is the correct answer.