It is reported in the newspaper that a man escaped from the prison last night and it was a long time

______ the guards discovered what had happened. [ ]

A. when          

B. until            

C. since        

D. before

制备黑膏药常选用的植物油是（）

A.菜籽油

B.大豆油

C.花生油

D.麻油

E.棉籽油