题目

—____ the workers are very tired, _____they keep on working.— They are great. We must learn from them. A . Because; / B . Though; / C . Because; so D . Though; but 答案：B随机抽取某班个学生,得知其数学成绩分别为,则右边的程序框图输出的表示样本的数字特征是                        （    ） A.中位数    B.平均数  C. 方差  D.标准差