题目

 —Why are most children under too much pressure? —Because their parents always compare them_____others. A.with      B.by     C.to    D.of 答案：A已知2A＋3B = C＋3D，又A和49 g B恰好完全反应，其生成57 g C和1 g D，，若B的相对分子质量为98，则A的相对分子质量为       A． 16       B． 27      C． 44      D． 56