There is a new park near Andy's home. It's fine today. Andy and his family are in the park now. On their left, there is a café. On the right, there is a big lake. There are many flowers and trees around the lake. There's a small hill behind the lake. Near the lake, there are two signs（标记）. One says, "Don't swim in the lake."But you can go boating on the lake. There is a beautiful garden in the middle of the park. There are green grass and beautiful flowers in it. There are some small shops between the lake and garden. The park is so nice. Andy and his family like it very much.

豚鼠的毛色有棕色和黑色之分，现有一棕色雄性豚鼠与黑色雌性豚鼠交配，产生的子一代都是黑色豚鼠（如下图）．请据图分析回答下列问题（用T、t表示控制毛色的显、隐性基因）：