若a=20.5,b=log20.5,c=log21.5,则( )
把 (a-1)2-9因式分解的结果是( )
Although many Americans move a lot, they still________and understand each other's dialects.
A:根据所给中文及句意,完成下列空格。(7分)B.用所给词的适当形式填空: (10分)