题型:填空题 ---How long has the train been away?---Sorry. I don’t know. By the time I got here, the train ________.A.has leftB.was leavingC.has been awayD.had left 查看答案
题型:填空题 近年来,我市积极探索建设新农村的服务体系,许多农户获得“测土配方施肥”服务,有效解决了施肥比例不合理问题,提高了农作物产量,减少对环境的污染。小明家种了一片麦子,经农科人员测定该片土壤需补充钾元素39kg,氮元素42kg。请你帮小明算算,至少需购买硝酸钾、硝酸铵各多少千克? 查看答案