51 下列有關汞齊合金之敘述:① gamma phase 指 Ag3Sn ② gamma 1 phase 指 Sn7Hg ③ gamma 2 phase 指 Ag2Hg3,何項錯誤? (A)僅 ① (B)僅 ② (C)僅 ③ (D)②+③