被称为地球之“肺”的是

假设某种植物的高度由三对等位基因A、a、B、b与C、c共同决定，显性基因具有增高效应，且增高效应都相同，并且可以累加，即显性基因的个数与植物高度呈正相关．已知纯合子AABBCC高60cm，aabbcc高30cm，据此回答下列问题．

（1）基因型为AaBBCc和aabbcc的两株植物杂交，F₁的高度范围是____ ．

（2）将F₁的最高株除去，其余与隐性个体测交，测交后代中高度类型和比例为　____ 

（3）F₁的最高株自交，F₂的表现型有____ 种．其中高度是55cm的植株的基因型有____ ，这些55cm的植株在F₂中所占的比例是____ ．

    We spend hours, days and years of our lives in school. Imagine(想象) you could design(设计) your dream school, what would it be like? What would you be doing? We wanted to find out what teenagers around the world thought. Here is what they said:

    Richard from the USA: My dream school would have a big swimming pool and two soccer fields. It would also have a cinema, a gym and a shopping centre. My school has none of these, and I think there should be more pleasant things for students to do while they are studying.

    Sonia from Italy: I'd like a room where we can relax and play computer games. I'd also like to have a music room. I think there should be a place for everyone to go and relax after class.

    Wu from Beijing: I think it would be great to have another day off (休息日) every week, besides the weekend. If that day was a Friday or a Monday, we would have a long weekend every week. What fun! I also think school should start later, at about 10 o'clock, and finish earlier.

    Hannah from Australia: In my dream school, I think the teachers should give us more freedom(自由) and choice about how we study and what we study. I also think it's not necessary for us to wear school uniforms every day. I really don't like wearing it.