求翻译：Naismith studied current(当前的) games. He found that all the most popular games used a ball. So a ball would be part of his new game, he decided. But kicking the ball or hitting it would be too rough for indoors. So he put two baskets up on poles. The players had to try to throw a soccer ball into them. Naismith then made thirteen rules for the game. Twelve of them are still in use today. Just seven years after the game began, professional basketball teams were formed.是什么意思？

待解决 悬赏分：1 - 离问题结束还有