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问题 填空题 案例分析题

果蝇的下列性状分别由位于两对常染色体上的两对等位基因控制，分别用A、a和B、b表示．且基因A具有纯合致死效应。巳知黑身残翅果蝇与灰身长翅果蝇交配，Fl为黑身长翅和灰身长翅，比例为l︰l。当F1的黑身长翅果蝇彼此交配时，其后代表现型及比例为：黑身长翅︰黑身残翅︰灰身长翅︰灰身残翅=6︰2︰3︰l。请据此分析回答下列问题：

F2中的黑身残翅果蝇个体测交后代表现型及比例为（）

答案

参考答案：黑身残翅：灰身残翅=1：1

单项选择题

In the United States and in many other countries around the world, there are four main ways for people to be (91) about developments in the news: newspapers, magazines, and radio or television news broadcasts. A person may use one, or all, of these (92) for information. Each source is useful in its (93) way. Newspapers and magazines can give much information about a particular event. They may (94) some history of the event, some of its (95) , some of its effects, or perhaps give an (96) or point of view on a particular development. Radio and television can help a person to be well informed about what is happening each day. It is also (97) to listen to radio or watch TV (98) do something else at the same time. Many people can listen to the news on their car radio while driving (99) . For the student of English as a foreign language, an English language newspaper may be the most helpful news source that will also (100) you practice in reading English.
Most daily English language newspapers are not very hard to find. They are interesting and helpful in many (101) . In some of them, you may be able to find news about your (102) country. You will find news and information about important national and international political (103) . (104) what you are interested in, you can probably find something in the newspaper about it. A(n) (105) in the newspaper may help you solve a problem. Other stories may be about good movies, concerts, or TV shows.
Usually, an English language newspaper has several (106) or parts. Each part of the newspaper (107) stories about different kinds of news. Some sections have a lot of advertisements which may be helpful if you want to save money. By reading the advertisements, you may find something you want (108) sale. Or you may find that two stories are advertising the (109) thing, but at one store the price is lower. Other sections may have (110) advertisements or have only a specific type of advertisement to interest the people.

A．fewer

B．more

C．less

D．same
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单项选择题

化合物半导体砷化镓常用的施主杂质是（）。

A.锡

B.硼

C.磷

D.锰
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