Teacher: 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.
Teacher: Now, understand the problem? If you are still confused, see the following example:
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 _ .
Reason: It is clearly mentioned in the article that to the check effect of mood on children is the main purpose of the experiment.

Now, solve this instance: Article: A farm planted levels or floors is called a vertical farm. A skyscraper type building can house a vertical farm. Since the garden is built upwards,rather than outwards,it requires much less space than a conventional farm. The world is quickly running out of room for conventional farming. Vertical farms could be a key to this situation. An 18story vertical farm could feed as many as 50,000 people,all in an area which is the size of the average city block. Vertical farms in the city could cut down on transportation costs as well. Think about the amount of fuel it takes to transport food from farmland to city. The resources saved would be surprising. Besides saving travel time,food would be delivered in fresher condition and with less damage. There is a growing concern about the use of pesticides in agriculture today. But the vertical farm would be a greenhouse type environment, avoiding the need for a large number of pesticides. Vertical farms can be built in a contained space,therefore they are an excellent solution for living well in an environment far different from our own. Hydroponics could be a big part of vertical gardening. This would reduce the amount of soil needed to grow food. Of course,not all food does well with this type of planting,but there are many crops that actually seem to do better. In some climates,a lack of sunlight creates a short growing season. The solar power option may not work as well here. The addition of grow lights would make it possible to grow crops in vertical gardens in these areas .In other words,we could grow crops in areas where we never could before. Vertical farms may just be a concept for now,but they are a concept that will solve many of our problems in the future.
Answer: is only an environmental friendly farm
Student:
According to the passage, a vertical farm _ .