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1. The picture is very invaluable because it was damaged during the war. ( Kết quả+ because+ Nguyên nhân)
2. Those students, who didn't do their homework, were punished. ( who thay thế và bổ sung ý nghĩa cho 'those students')
3. Because it rained heavily, we didn't go to the party. ( Because+ mệnh đề)