Soccer is the most popular sport in the world. Unlike other sports, soccer does not require very much equipment. The field can be any size, goal posts can be makeshift, and anything that can be kicked can serve as the ball. Ttherefore, it is entirely unsurprising that the most recent FIFA World Cup -- the largest international soccer tournament -- attracted more than three billion viewers, which was a world record. The argument depends on which one of the following assumptions? ["Soccer is relatively less popular in the United States due to the country's prosperity.", 'People who play a sport are likely to be fans of that sport.', 'Other sports would be similarly popular if they could reduce their economic cost.', 'Soccer is the most popular in South America and Europe.']