6. 下列何者直接由掌深弓(deep palmar arch)分枝而來? (A)指掌側總動脈(common palmar digital artery) (B)掌骨掌側動脈(palmar metacarpal artery) (C)指掌側固有動脈(proper palmar digital artery) (D)食指橈側動脈(radialis indicis artery)