红灯熄灭后眼睛里出现了蓝绿色的后象．这叫（）
A.正后象
B.负后象
C.明度对比
D.彩色对比
参考答案：B
Which of the following statements about object oriented database is NOT correct
A．Each object has a unique object identity in the system
B．Encapsulation and inheritance are two important features of object oriented database
C．A subclass can inherit the attributes and methods of all its superclasses
D．A superclass includes the attributes and methods of all its subclasses
火山灰质水泥适用于配置耐碱混凝土。
