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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: Foreign attacks on U. S. soil 1812 ---- During the War of 1812, British forces burned the new capital at Washington, D. C. They also attacked Baltimore and New Orleans and captured Detroit, which at the time was a remote military outpost . 1846 ---- A brief invasion by Mexican troops across the Rio Gande began the U. S. - Mexican War in 1846. But the remaining action in that conflict occurred in California, New Mexico and in Mexico. California and New Mexico belonged to Mexico at the time. 1916 ---- Mexican revolutionaries led by Pancho Villa attacked the town of Columbus, N. M., on March 9, 1916. 1941 -- Japan attacked Pearl Harbor in Hawaii on Dec. 7, 1941, killing nearly 2,400 people and forcing America into World War II. 1993 ---- Terrorists blew up a truck bomb in the basement of the World Trade Center in February 1993, killing six people and injuring more than 1,000. 2001 ---- Terrorists hijacked several planes on Sep.11, 2001. Two ploughed into New York's World Trade Center (WTC), _ the two highest buildings in the city; a third seriously damaged the Pentagon . The fourth hijacked plane crashed in Pennsylvania. Several thousand people were killed in the attacks.
Answer: destroyed the Pentagon completely
Solution:
During the September 11th terrorist attacks, _ .