1. (should) give up the jon (từ "jon" có phải viết sai không bạn?)
2. learned Korea since he was ten (thì hiện tại hoàn thành, since + mốc thời gian)
3. of earing a small salary, he is happy (Although + S + V = In spite of + V_ing)
4. don't we visit museum next Sunday? (Let's = Why don't + S + V (nguyên thể)