In a ______ country like this, no one should go hungry.
查看答案
The old man lived a ______ life after his retirement.
Leisure in our society is often defined ______ work.
Social ______ , in short, means the movement of a person or a group from one social class to another within a given society.
Millions of years ago, changes in the earth's climate caused animal and plant life to ______ .