题目

Do you usually pay much attention to the nutrition facts on packages of food and drinks? Two students, Anna and Jenny, in New Zealand did. They also discovered a    21    about a popular local drink. The science experiment   22   the two 17-year-old girls showed that the blackcurrant (黑醋栗) drink, Ribean, contained almost no vitamin C. However, its    23   ,the world's second-largest food and drug company GlaxoSmithKline had made claims (宣称) to the   24    in their ads.     The students, then 14, decided to   25    the vitamin C levels of their甲、乙两种冬小麦试验品种连续5年的平均单位面积产量如下（单位：t/hm2）品种第1年第2年第3年第4年第5年甲9.89.910.11010.2乙9.410.310.89.79.8其中产量比较稳定的小麦品种是     ．