A:100ml0.5mol/LMgCl2溶液
B:200ml0.25mol/LHCl溶液
C:50ml1mol/LNaCl溶液
D:200ml0.25mol/LCaCl2溶液
中国近代史,既是一部救国探索史,也是一部思想解放史。据此回答下列问题:
如果代数式a +1ab 有意义,那么直角坐标系中点A(a,b)的位置在( )
It will be 20 years since Hong Kong returned to China on July 1,1997.(就划线部分提问)
____ ____years will it be since Hong Kong returned to China on July 1, 1997?