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In this task, you're given an article and an answer. Your task is to generate the fill-in-the-blank question for this answer based on the given article. The blanks are always at the end of the question, and can be filled with more than one word or phrase.

Article: Homework can put you in a badmood , and that might actually be a good thing. Researchers from the University of Plymouth in England doubted whether mood might affect the way kids learn. To find out the answer, they did two experiments with children. The first experiment tested 30 kids. Someshapes were hidden inside a different, larger picture. The kids had to find the small shapes while sitting in a room with either cheerful or sad music playing in the background. To test their mood, the scientists asked the kids to point to one of five faces, from happy to sad. Children who listened to cheerful music tended to point to the smiley faces while the others pointed to the unhappy ones. The researchers found that sad kids took at least a second less to find the small shapes. They also found an average of three or four more shapes. In the second experiment, 61 children watched one of two scenes from a film. One scene was happy, and the other was sad. Just like in the first experiment, kids who saw the sad scene acted better compared to the others. The researchers guessed that feeling down makes people more likely to focus on a problem or difficult situation. Not all scientists agree with them, however. Other studies argued that maybe, that cheerful music in the first experiment distracted kids from finding shapes. While scientists work on finding out the answers, it still might be wise to choose when to do your tasks according to your mood. After eating a delicious ice cream, for example, write an essay.
Answer: whether mood affects their learning ability
Solution: Researchers did experiments on kids in order to find out _ .
Why? It is clearly mentioned in the article that to the check effect of mood on children is the main purpose of the experiment.

New input: Article: The color red often means danger --- and by paying attention, accidents can be prevented. At railroad crossings, flashing red fights warn cars to stay back. A red light at a traffic crossing tells cars to stop, so they don't run into other cars. In the future, the color red also may help prevent danger at construction sites. Thanks to new work by engineers, bridge supports --- or other kinds of materials --- could one day contain a color-changing material. It will turn red before a structure collapses or falls apart. The secret behind the color-changing material is a particular type of molecule . Molecules come in all shapes and sizes, and make up everything you can see, touch or feel. How a molecule behaves depends on what kinds of atoms it contains, and how they're held together. To get a rough picture of one way atoms are held together in a molecule, imagine you and your friends standing in a large circle, holding hands. Each person represents one atom, your clasped hands represent the bond, and the entire circle represents a molecule. The molecule being used to turn the material red is called mechanophore . When one chemical bond in the mechanophore molecule breaks, the rest of the molecule turns red. There is a way to get rid of~ the red color: light. When a bright light is shone on the mechanophore, the broken bond is fixed and the red color disappears. This "self-healing" may be a problem for engineers who want to use the color-changer in big construction projects that will be outside, in the sunlight. And if bright light keeps the red color from appearing, then the mechanophore's warning system will be useless. Scientists still have a lot of work to do before the color-changing molecules can be used outside the lab. If mechanophore can be used in the real world, they are suggested to be employed in a new kind of paint.
Answer: warn people that the building is dangerous
Solution:
The color red will be used at construction sites to _ .