Over years,scientists have made a great________in the treatment of cancer.
A:breakin
B:breakthrough
C:breakup
D:breakdown
如图,在⊙O中,直径CD垂直于弦AB,若∠C=25°,则∠BOD的度数是( )
农作物的种子经过发酵、蒸馏制得的乙醇被称为“绿色汽油”.乙醇的分子结构如图所示.则下列叙述正确的是( )