一个完整的能完成能量传递的液压系统是由（）元件、（）元件、（）元件和（）元件组成。
参考答案：动力；控制；执行；辅助
The food is not very good in this restaurant,but we shall just have to ________ it.[ ]
A. pay attention to
B. hold on to
C. put up with
D. keep up with
固体废物的环境问题？
