The word they” in paragraph refers to .

Read the following passage and mark the letter A, B, C, or D to indicate the answer to each of the question.
Though gambling is typically associated with casino games, strategic sport betting is rapidly gaining in popularity – and that's a whole other ball game, Prof. Dannon explains. "Sports gamblers seem to believe themselves the cleverest of all gamblers. They think that with experience and knowledge – such as player's statistics, manager's habits, weather conditions, and stadium capacity – they can predict the outcome of a game better than the average person."
But in a study published in the journal Psychopathology, Prof. Dannon and Dr. Ronen Huberfeld of the Beer Yaakov Mental Health Center determined that neither betting experience nor knowledge of the arcane details of the game is connected to successful betting outcomes. Indeed, he says, the two most successful gamblers in their study had no prior experience in gambling or knowledge of the sport in question. This should inform how psychologists approach sports gamblers, who need to be treated using different methods than their casino-addicted counterparts. For their study, the researchers focused on the field of soccer betting, one of the most popular and growing forms of sports gambling. They recruited three groups of participants, including 53 professional sports gamblers, 34 soccer fans who were knowledgeable about the sport but had never gambled, and finally, 78 non-gamblers with no prior knowledge of soccer at all. All participants were asked to place bets on the final scores of the 16 second-round matches of the Champion's League, organized by the Union of European Football Associations. This model mimics how gamblers actually put their money on the games, where they need to bet on exact scores to win.
Although those who had prior knowledge of soccer were expected to have a higher success rate, the researchers discovered that, in fact, their success rate was no better than those of the other two groups. Interestingly, the two participants with the most successful record, correctly betting on seven out of the 16 games each, hailed from the group with no prior understanding of the sport.
This doesn't indicate that there is an advantage to inexperience, says Prof. Dannon – many others in the third group were unable to predict any of the results correctly. But the outcome exposes the myth of knowledge as a powerful betting advantage. The sense of control that encourages sports gamblers in their betting is just an illusion.
(Source: https://www.sciencedaily.com/)