2011年，是纪念辛亥革命多少周年（   ）

2015年第九号台风“灿鸿”来袭，中央电视台发布台风黄色预警信息。人们能够根据台风预警信息，将台风带来的损失降到最低。这说明人能够（    ）

某种山羊的有角和无角是一对相对性状，由一对等位基因（A、a）控制，其中雄羊的显性纯合子和杂合子表现型一致，雌羊的隐性纯合子和杂合子表现型一致．多对纯合的有角雄羊和无角雌羊杂交，F₁中雄羊全为有角，雌羊全为无角；F₁中的雌雄羊自由交配，F₂的雄羊中有角：无角=3：1，雌牛中有角：无角=1：3．请回答下列问题：

（1）控制该相对性状的基因位于____  （填“常”或“X”）染色体上；这对相对性状中____  （填“有角”或“无角”）为显性性状．

（2）请对上述实验结果做出合理的解释：

①这对相对性状的遗传遵循____ 定律．

②相同的基因型在公羊和母羊中的表现型可能不同：在公羊中，____ 基因型决定有角，____ 基因型决定无角；母羊中，____ 基因型决定有角，____ 基因型决定无角．

（3）若上述解释成立，F₂无角母羊中的基因型及比例是____ ．

（4）为了验证（2）的解释是否成立：让无角公羊和F₁中的多只无角母羊交配，若子代____ ，则（2）的解释成立．

（5）上述探究过程体现了现代科学研究中常用的一种科学方法，叫做____．

    Everyone needs friends. But how do you find real friendship and keep it?

    The American writer Sally Seamans tells young students some smart ways to find friends. Sally says founding friendship is just like planting a tree. You plant the seed (种子) and take care of it to make it grow.

    First, you should choose a friend. What makes a good friend? It is not because a person has money or good looks. A good friend should be kind and patient. For example, if you have a bad day, a good friend could listen to your complaints (抱怨) and do his or her best to help you. To make a friend, you can't be too shy. You should make each other happy and share your lives.

    But things can not always be happy. Even the best friends have fights. What should you do when you have a fight with your friend? You have to talk to him or her. When there is no one around, have a good talk. If he or she doesn't want to talk, you can write a letter.

    There are three steps to be friends again:

    Tell him or her how you are feeling, say what your friend did wrong and talk about why you did this or that. Remember that friendship is one of the most important things in your life.