28. The correct answers are B and D. The word "so" should be corrected to "because" in option B, and the word "in" should be corrected to "from" in option D. The correct sentence should be: "Nam is far from his family, because he remembers his parents from his hometown so much."

 

29. The correct answer is C. The word "using" should be corrected to "to use" to make the sentence grammatically correct. The correct sentence should be: "It is important for parents to teach their children how to use social media wisely."

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