CuSO4·5H2O的俗名是（ ）
A：食盐
B：烧碱
C：胆矾
D：纯碱
若A，B，C是直线存在实数x使得x2OA→+xOB→+BC→=0→，实数x为（ ）
“横七竖八”指的是____，带有“七、八”的成语有____。
We will hear what he must say and observe what he will do for what he says and what he does often _______.
