51.金屬瓷修復體(metal-ceramic restorations)在烤瓷前,須先氧化鑄體合金,此過程稱為何者?①條件化燒烤(conditioning bake) ②除氣(degassing) ③氧化還原(oxidization-reduction) (A)僅①② (B)僅①③ (C)僅②③ (D)①②③