题目

 In the United States and several other countries, 2.5 million children play baseball in an organization called Little League. They play on teams in their hometowns. Their parents and other adults in the community coach or instruct them and serve as umpires to make sure that everyone follows the rules. Local businesses give money for the ball fields and the uniforms. Local teams compete against each other and the winners get to play teams that are more distant. Eventually, the top teams go to the Little League World Series. One hundred years after Abner Doubleday invented baseball in 如图，小明用一个透镜观看书上的一个英文单词，他看到了两个字母“YS”的放大的像．这个透镜是________透镜，这种透镜对光线有________作用，利用这种透镜可制成的光学仪器有________(只需填写一种)．