工人根据设计蓝图施工时，主要依赖于______。
A．创造想象
B．再造想象
C．无意想象
D．记忆表象
参考答案：B
Go on with your English study. _____ is difficult if you put your heart into it. [ ]
A. Anything
B. Something
C. Nothing
有效边界上的点对应的证券组合称为有效组合。( )
