The earth is changing. Tomorrow it will be different. All the living things on the earth are changing. Even people are changing, and tomorrow you will be different. There are many kinds of change, and many different things than cause change. People need to realize the changes, to learn to see them, and to learn what causes change. Human beings must solve many problems so that they can continue to live successfully. War is one of these problems. Disease and natural _ are problems. Having enough food and energy for the growing number of people in the world is a problem. Most problems can be solved, but some are impossible to solve. The way in which people solve problems affects how long and how well they can live. As people solve their problems, they change things, and changes often cause new problems for people and for other living things on the earth. Sometimes the new problems seem even worse than the old ones. Human beings will probably never stop having problems to solve. Can you use your imagination to describe a world that has no problems at all ? The reason why everything is changing is that  _  .
people want them to be changing there're many different things that cause them to change the living things are changing the world is too small