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.

Example input: 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
Example output: Researchers did experiments on kids in order to find out _ .
Example explanation: It is clearly mentioned in the article that to the check effect of mood on children is the main purpose of the experiment.
Q: Article: It is easy for us to find that Mexico has so many neighbors. The United States is to the north while Guatemala and Belize are to the south. Mexico is about one quarter of the size of the United States with the population of more than ninety million people. The language of Mexico is Spanish, which makes Mexico the world's largest Spanish-speaking country. Mexico City is the capital and largest city of Mexico. The city is also very high. It is 7349 feet high (2240 meters), making it one of the highest capital cities in the world. The population, of Mexico City grows bigger every day. About thirty million people live there. It has more people than any other city in the world, even more than Tokyo. Mexico also has its specialties. Many of the foods we eat started in Mexico such as beans, maize, avocados, tomatoes, peanuts, chili peppers, vanilla, and chocolate. Mexico is also famous for its cactus plants and has more kinds of cactus than any other country.
Answer: on the north of
A:
Mexico is _ the USA.