材料是能被人类经济地用于（）的物质。
A、实现功能
B、建筑
C、设计搭建
D、制造有用物品
参考答案：D
Zhanglin was lost in computer games during his last year in high school, otherwise he _____ a student at Beijing University.
A．would have been
B．can be
C．has been
D．had been
低温冷却转换开关置“自动”位时，当温度达到（）时，温度继电器动作，打开低温百叶窗。
A、60℃
B、65℃
C、70℃
D、75℃
