问题 填空题

如图所示是一台投影机的示意图.其中A是 ______,A的作用是 ______.B是 ______,B的作用是 ______.

答案

A是平面镜,平面镜的作用是由凸透镜折射的光线通过平面镜反射到银幕上.

而凸透镜的作用在这里就是成物体的倒立、放大的实像.

故答案为:平面镜;改变光的传播方向;凸透镜;利用凸透镜成像.

单项选择题
阅读理解

阅读理解

     What will people die of 100 years from now? If you think that is a simple question, you have not been

paying attention to the revolution that is taking place in bio-technology(生物技术). With the help of new

medicine, the human body will last a very long time. Death will come mainly from accidents, murder and

war. Today's leading killers, such as heart disease, cancer, and aging itself, will become distant memories.

     In discussion of technological changes, the Internet gets most of the attention these days. But the change in medicine can be the real technological event of our times. How long can humans live? Human brains

were known to decide the final death. Cells(细胞) are the basic units of all living things, and until recently,

scientists were sure that the life of cells could not go much beyond l20 years because the basic materials of cells, such as those of brain cells, would not last forever. But the upper limits will be broken by new

medicine. Sometime between 2050 and 2100, medicine will have advanced to the point at which every 10 years or so, people will be able to take medicine to repair their organs. The medicine, made up of the basic building materials of life, will build new brain cells, heart cells, and so on-in much the same way our bodies make new skin cells to take the place of old ones.

     It is exciting to imagine that the advance in technology may be changing the most basic condition of

human existence, but many technical problems still must be cleared up on the way to this wonderful future.

1. The author thinks the question how people die in the future __________.

A. is simple

B. is funny

C. has something to do with bio-technology

D. has something to do with environment

2. According to the passage, human death IS now mainly caused by       .

A. diseases and aging  

B. accidents and war

C. accidents and aging  

D. heart disease and war

3.In the author' s opinion, today's most important advance in technology lies in         .

A. medicine  

B. the Internet

C. brain cells   

D. human organ

4.Humans may live longer in the future because         .

A. heart disease will be far away from us

B. human brains can decide the final death

C. the basic materials of cells will last forever

D. human organs can be repaired by new medicine

5.We can learn from the passage that        .

A. human life will not last more than 120 years in the future

B. humans have to take medicine to build new skin cells now

C. much needs to be done before humans can have a longer life

D. we have already solved the technical problems in building new cells