山东农业工程学院图书馆拥有独立的光纤网络。

—How I wish I had studied harder when I was in senior school!

—If you had, you _____ a university student now.[ ]

A. are  

B. would be

C. should  

D. were

除去下列各物质中括号内的杂质，所用试剂正确的是[ ]

A．NaCl（Na₂CO₃）溶液，用适量BaCl₂溶液

B．FeSO₄（CuSO₄）溶液，用适量锌粉

C．H₂SO₄（HCl）溶液，用适量NaOH溶液

D．CaCl₂〔Ca(OH)₂〕溶液，用适量稀盐酸

爆破作业必须严格执行哪些制度？