题目

某生物兴趣小组同学做了“探究菜豆种子萌发的环境条件”实验，在1号、2号、3号、4号四个烧杯中分别放等量的餐巾纸，再将相同数量的菜豆种子放在上面，在不同条件下进行培养。数日后记录发芽情况如下：烧杯种子所处环境实验结果1号干燥的餐巾纸，置于25℃橱柜中种子不萌发2号潮湿的餐巾纸，置于25℃橱柜中种子萌发3号潮湿的餐巾纸，置于冰箱冷藏室（4℃）？4号餐巾纸和种子全部浸泡在水中，置于25℃橱柜中种子不萌发（1）设置2号烧杯的作Experiment of this kind________in both the U．S. and Europe well before the Second World War. A. have conducted  B. have been conducted C. had conducted  D. had been conducted