Choose your answer from: (1). By studying brain scan results of the groups.; (2). By comparing the performances of different groups.; (3). By asking and observing people in different groups.; (4). By analyzing the amount of tasks each participant did.;

Read the following article and answer the question. Article: Have you ever been stuck for hours on a hard math problem? If you sat there for some time you might eventually solve it, but scientists say that daydreaming might be a much better way to tackle difficult tasks. In fact, daydreaming has long been misunderstood. It's considered to be a bad thing and often associated with laziness. "We're harsh on ourselves if we catch ourselves mind wandering," says Professor Kalina Christoff from the University of British Columbia in Canada. But the truth is that some of the most important scientific discoveries came about because scientists allowed their minds to wander. For example, Albert Einstein began his theory of relativity when he daydreamed about riding a beam of sunlight to the edge of the universe. And now, research has shown that normal people can also improve their problems solving ability in the same way, reported The Telegraph. In a study, 145 people aged between 19 and 32 were asked to list as many unusual uses as possible for everyday objects. Some of them were given a 12-minute break while the others were not allowed any break from the task. People on the break did not simply relax--some of them were told to carry out a tiring memory task while others did an easier task. Scientists found that people who did the easier task were daydreaming a lot. They thought about personal issues in the past or in the future because their mind was at ease. After the break, all participants were asked to return once again to the task of listing unusual uses for everyday objects. It was found that daydreamers improved their performance by 40 percent, while all the other people, including those who didn't have a break and who did tiring tasks during the break, performed the same as before. "People think that when the mind wanders away, it just gets turned off--but we show the opposite," explained Christoff."A more playful attitude might allow you to call in more resources ." So when you are struggling to solve complicated problems, it might be better off if you switch to a... Question: . How did the scientists get their conclusion? Answer:
Answer:
(2).