Todaythereare6billionpeopleontheearth.Bytheyear2050t...
问题详情: Todaythereare6billionpeopleontheearth.Bytheyear2050theremaybe12.5billion.Thisisalotofpeopletofeed.Weneedmorefood. Onewaytoproducemorefoodisbygrowingstrongerplants.Forthousandsofyear...