Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions.

Are sports bad for kids? People think children should play sports. Sports are fun, and playing with others. However, playing sports can have negative effects on children. It may produce feelings of poor self-respect or aggressive behavior in some children. According to research on kids and sports, 40,000,000 kids play sports in the US. Of these, 18,000,000 say they have been yelled at or called names while playing sports. This leaves many children with a bad impression of sports. They think sports are just too aggressive. Many researchers believe adults, especially parents and coaches, are the main cause of too much aggression in children's sports. They believe children copy aggressive adult behavior. This behavior is then further strengthened through both positive and negative feedback. Parents and coaches are powerful teachers because children usually look up to them. Often these adults behave aggressively themselves, sending children the message that winning is everything. At children's sporting events, parents may yell insults at other players or cheer when their child behaves aggressively. As well, children may be taught that hurting other players is acceptable or are pushed to continue playing even when they are injured. In addition, the media makes violence seem exciting. Children watch adult sports games and see violent behavior replayed over and over on television. As a society, we really need to face up to this problem and do something about it. Parents and coaches should act as better examples for children. They also need to teach children better values. They should teach children to enjoy themselves whether they win or not. It's not necessary to knock yourselt out to enjoys sports. Winning isn't everything. In addition, children shouldn't be allowed to continue to play when they are injured. Sending a child with an injury into a game gives the child the message that health isn't as important as winning. If we make some basic changes, children might learn to enjoy sports again.

Which is described as the main cause of more aggressive playing?