题目

–I must apologize for _____ ahead of time.  –That's all right. A. letting you not know                   B. not letting you know C. letting you know not                    D. letting not you know 答案：B在小麦品种的试验中，甲、乙两种冬小麦试验品种连续5年的平均单位面积如下：则甲、乙两组数据中较小的方差s2=______