The news that a jet __________ Russian mountains killing 88 was one of the worst things I have known in the past five years.[      ]

A. crashed down  

B. crashed into

C. met with 

D. came across

Westgard质控图与Levey-Jennings图的主要区别是前者（）

A.可以区分系统误差和随机误差

B.同时测定低值及高值两个质控品

C.考虑了“多个”质控规则

D.使用测定值的标准差做图

E.以选定变异系数做图