题干

下列各项中,不可能出现如图结果的是(    )

A:具有一对相对性状的杂合子植物自交所产生后代的性状分离比

B:一个次级卵母细胞形成的极体与卵细胞的数目之比

C:杂合红眼雌蝇与红眼雄蝇杂交产生后代的性状分离比

D:15N的DNA分子放在含14N的培养液中复制三次后,不含15N的DNA分子与含15N的DNA分子之比

上一题 下一题 0.0难度 选择题 更新时间:2015-12-09 07:07:50

答案(点此获取答案解析)

B

同类题3

阅读下面材料,从每题所给的A、B、C、D四个选项中选出最佳选项。

     I am off on a trip on my own. Yes ! Alone! I can't wait to get going to Europe to see some cities I really want to visit. It is great because I can choose what I want to do in each city. I am going to travel by train on the Eurorail.

     The train trip was fast and the views of the countryside were amazing. Now I am in Salzburg, Austria. The quiet hills of Austria are a great place to relax. The movie The Sound of Music was filmed around this area. Mozart, the famous musician, was from here. I listened to some of his classical music.

     The train ride to Amsterdam was a long one. It gave me time to write some postcards to send back home. Amsterdam is a fun city, full of friendly locals and many tourists. I spent the whole day visiting the art museums here. The museum about the famous Dutch artist Van Gogh is filled with history and beautiful art. I took a boat ride and saw local people in traditional dress. I even got to taste some delicious Dutch cheese.

     Copenhagen, Denmark, is one of the safest places in the world. I spent a busy and nice day at the Tivoli Amusement Park. It is a huge park which even has concerts and dance shows. Hans Christian Anderson, a famous writer of children's books, was born in this city. I found a lovely bookshop and bought two of his fairy tale books, The Little Mermaid and The Ugly Duckling. My travels alone are done! What an adventure this trip has been! I love it.