常用的前牙充填材料是
A．磷酸锌粘同粉B．氢氧化钙C．复合树脂D．银汞合金E．聚羧酸锌粘同粉
参考答案：C
机器造型的模样，有时在水平芯头靠近模样的根部，设置一道凸起的圆环，这道圆环叫做（）。
A.集砂槽
B.特殊芯头
C.压环
D.防压环
Mary often does some translation work to earn extra money, which ________ half of her income.
[ ]
A. makes up
B. counts on
C. accounts for
D. consists in
