Read the following article and answer the question. Article: You may think that inventions are far away from your everyday life. But in fact, almost everyone can invent. It's just that they do not recognize that their idea could be the start of an invention. Once inventors see their ideas have some practical value, they don't let them slip away. For example, the inventor of the dishwasher, American Josephine Cochrane, loved to give dinner parties. But she found it took too long to wash her dishes by hand and too many of them broke. She decided that a machine could do the job faster and with fewer mistakes. So, in 1886, she set out to make one for herself. Like Cochrane's, most inventions are created to solve a problem. So, the first and most important step is to find the problem. You can start by looking at what is wrong with things you use now. You can ask grandparents or neighbours if they remember ever saying: "I wish someone would invent something for..." Or you can look at people in different areas such as on the street, or at school. Then you might notice situations or things in need of improvement. Remember to record your ideas and work. This will help you develop your invention and protect it when it is completed. The next step is to think about possible solutions. An invention is a new way of solving a problem. So think of many, varied, and unusual ways. You can often come up with a solution for a problem by looking at it from a different angle or thinking about it in a new way. Example 1 -- instead of thinking of shoes as protecting your feet from the ground, think of using something to protect the ground from your feet. Example 2 -- instead of thinking about how you can carry oranges home from a store, think of how they can come to you by delivery or growing your own. Example 3 -- instead of experimenting with only one solution, can you put two or three solutions together, or arrange them in different orders? And if one solution doesn't work, can it be put to other uses? That was how yellow post-it... Question: The main idea of this story is _ . Answer:

Pick your answer from: 1). how to put your ideas to other uses; 2). that you can invent and how you will be able to do so; 3). problem-solving technique; 4). how inventors invent;
The answer is:
2).