动机
参考答案：
动机是人们以愿望、兴趣、理想等形式表现出来的激励行为的主观因素。
_____you don’t lose heart, it will be easy for you to overcome the difficulties.
A．As well as
B．So long as
C．So far as
D．As soon as
蒸馏与分馏有何等区别？
