61岁男性，来院就医，口内检查，牙周组织健康，余留牙无松动，无倾斜也未见明显倒凹，取模作整铸支架可摘局部义齿修复

避免在制作可摘局部义齿中损伤模型，灌注工作模型的材料最好采用（）

A.磷酸盐

B.琼脂

C.普通石膏

D.硬石膏

E.超硬石膏

In students' eyes, a good teacher should have many good virtues, but _____, he or she should be knowledgeable. [ ]

A. above all

B. after all

C. first of all

D. in all