在进行任何C++流的操作后，都可以用C++流的有关成员函数检测流的状态；其中只能用于检测输入流状态的操作函数名称是

A．fail

B．eof

C．bad

D．good

If a developmental psychologist believes that 6-year-olds solve logical problems more efficiently and accurately than 3-year-olds because their memory holds more information and works more rapidly, this belief is consist with which of the following theories()

A．Information processing

B．Erickson

C．Kohlberg

D．Piaget