血清抗体效价的平均水平计算常用（）
A.算术均数
B.中位数
C.几何均数
D.全距
E.相对比
参考答案：B
This school doesn't have ______ it did ten years ago. [ ]
A. so many students as
B. many as students as
C. such few students as
D. so many as students as
手工调拌包埋材料，不正确的方法是（）。
A.调拌要求在60～120秒内完成
B.洗净橡皮碗，不用将水擦干，立即调拌包埋材料
C.调拌约120次
D.先将包埋料放入橡皮碗中，再将液体倒入
E.以上都不正确
