现取3个基因型不同的白色纯合品种甲、乙、丙分别与红色纯合品种丁杂交，实验结果如图所示，请回答：

已知两圆相切，圆心距为5cm，若其中一个圆的半径是3cm，则另一个圆的半径是（   ）

根据短文内容，选择正确答案。

Every four years, the greatest athletes from all over the world get together in one city to take part in the world sports meeting—the Olympic Games. The holy flame (圣火) is carried from one place to the next. In 2008, the holy flame was carried to Beijing, the capital of China.

When Beijing was chosen as the host city to hold the Olympic Games in 2008, all the Chinese people were very happy, excited and proud. They showed their excitement in different ways when they heard the news. Some people cheered, jumped and shouted.

    In Beijing we built a new Olympic village with hotels for athletes and stadiums for matches.

    "One World, One Dream" is our slogan for the 29th Olympics. It expresses the wishes of 1.3 billion Chinese people for a peaceful and better world tomorrow.