Concept:Pronoun must agree in number with its antecedent noun.Explanation:The noun "South Korea" is singular.The pronoun "their" in part (c) is plural and does not agree.The correct pronoun should be the singular "its".Thus, the error is located in part (c) of the sentence.Parts (a) and (b) contain no errors.The corrected sentence reads: "Since he was going to live in South Korea for some time, he thought he should learn something about its culture."Answer:(c)