Kế tên một số cây trồng vụ đông và nêu ý nghĩa của việc đưa vụ đông thành vụ chính ở Dồng bằng sông Hồng.

Trình bày đặc điểm dân cư, xã hội và những thuận lợi, khó khăn đối với sự phát triển kinh tế- xã hội ở Đồng bằng sông Hồng.

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