1. Changefulness and the complexity of network environment, as well as the frailty of information system, have decided the objective existence of network safe threat.

2. And it also makes a detailed analysis of the problems of uncertainty, complexity and changefulness in experimental data, and puts forward some relevant solutions.

3. The world owes much of its beauty to cloudland. The unchanging blue of the Italian sky hardly compensates for the changefulness and glory of the clouds.

4. When we analyze music works, we cannot ignore it for its shortness and changefulness. We should take a strict and scientific attitude and method towards analyzing and studying it.

5. Well I think that we should always call matter 'time matter' or matter of time so that we never for a moment forget its essential temporality and essential changefulness.