题干

如图为基因型为AaBb的个体在进行有性生殖时的过程,下列有关说法正确的是(  )

A:基因的分离定律发生在①过程,基因的自由组合定律发生在②过程

B:雌雄配子结合方式有9种,子代基因型有9种

C:F1中不同于亲本的类型占 716

D:F1个体产生各种性状是细胞中各基因随机自由组合选择性表达造成的

上一题 下一题 0.0难度 选择题 更新时间:2012-09-22 11:08:05

答案(点此获取答案解析)

C

同类题3

根据短文理解,选择正确答案。

    In choosing a friend, one should be very careful. A good friend can help you study. You can have fun together and make each other happy. Sometimes you will meet fair­weather friends. They will be with you as long as you have money or luck,but when you are down, they will run away. How do I know when I have found a good friend? I look for certain qualities of character,especially understanding, honesty and reliability(信任).

    Above all else, I look for understanding in a friend. A good friend tries to understand how another person is feeling. He is not quick to judge. Instead, he tries to learn from others. He puts himself in the other person's place, and he tries to think of ways to be helpful. He is also a good listener.

    At the same time, however, a good friend is honest. He does not look for faults in others. He notices their good points. In short, a friend will try to understand me and accept me.

    Another quality of a friend is reliability. I can always depend on a good friend. If he tells me he will meet me somewhere at a certain time, I can be sure that he will be there. If I need a favor,he will do his best to help me. If I am in trouble, he will not run away from me.

    There is a fourth quality that makes a friend special. A special friend is someone with whom we can have fun. We should enjoy our lives, and we would enjoy our friendship. That is why I especially like friends who are fun to be with. A good friend likes the same things I like. We share experience and learn from each other. A good friend has a good sense of humor too. He likes to laugh with me. That is how we share in the joy of being friends. And I know that he is looking for the same quality in me.

    When I meet someone who is reliable, honest, and understanding,I know I've found a friend!