She____thirteen years old．

在一个不透明的口袋中，装有5个红球3个白球，它们除颜色外都相同，从中任意摸出一个球，摸到红球的概率为（     ）

    I am a student. I like sports. I run every morning and I swim twice a week(一周两次). I like all kinds of ball games. I like football, basketball, volleyball, tennis and ping­pong. I am good at playing ping­pong. I often play ping­pong with my friend, Li Lei. We are on the school team. But he doesn't like any other ball game. He also likes to collect(收集)balls. He has a great collection(收藏品)of balls. He has 60 footballs, 16 volleyballs and many ping­pong balls. We like to watch sports on TV.

在题后的横线上简要说明下列不正确的实验操作会造成的不良后果