托帕石与海蓝宝石的区别：（）.
A.密度有区别
B.颜色色调有区别
C.托帕石为一轴晶，而海蓝宝石为二轴晶
参考答案：A, B
Lucy looks unhappy today. Let’s give her this present _________ .
A．to cheer her up
B．cheer her up
C．cheer up her
D．to cheer up her
下列哪项不是铸造支架的优点
A．无异味
B．异物感小
C．设计不灵活
D．导热好
E．坚固
