With _____ help of my teacher, I have made great progress.
A:the
B:a
C:an
D:/
袋中有5个红球、4个白球、3个黄球,每一个球除颜色外都相同,从袋中任意摸出一个球是白球的概率( )
“一国两制”构想中最重要的前提是( )