赫尔巴特认为教学过程是新旧观念的______和______的过程。
参考答案：联系，系统化；
By the time Fred gets back home, his girlfriend for London to study.
A．will have left
B．leaves
C．has left
D．will leave
脱碳工序要求将合成气中的CO2浓度降至（）以下。
A.0.01%
B.0.10%
C.1.00%
D.0.001%
