题型:选择题 She lost herself in watching the leaves _____ in the wind. [ ]A. dancing B. swimming C. hanging D. dropping 查看答案
题型:选择题 - Was it because of his laziness_______ he didn't do the experiment successfully?- No, it was because of his carelessness.A.thatB.whileC.forD.as 查看答案
题型:多项选择题 如图,曲线a表示使用诱变剂前青霉菌菌株数和青霉素产量之间的关系,曲线b、c、d表示使用诱变剂后菌株数和产量之间的关系。下列说法正确的是()A.由a变为b、c、d体现了变异的不定向性B.诱变剂决定了青霉菌的变异方向,加快了变异频率C.青霉菌在诱变剂作用下发生的变异可能有基因突变和基因重组D.d是最符合人们生产要求的变异类型 查看答案