B．is too complex to be reproduced

　　C．may change a lot in 10 or 20 years

　　D．will soon be replaced by machines

　　解析：选A　细节理解题。由第一段中的"as complex as the human brain"和"as intelligent as the human brain"可知，作者认为人类的大脑十分复杂而且非常聪明，故选A项。

　　5．The underlined word "carbon" in Paragraph 2 stands for________.

　　A．human beings B．an old machine

　　C．an ocean animal D．intelligent robots

　　解析：选A　细节理解题。由该段中的"machines of silicon will arise to compete with their human ancestors"可知，carbon 在此是指代人类(碳基生命是以碳元素为有机物质基础的生物，地球上已知的生物，包括人类在内，大多数都是碳基生命)，故选A项。

　　6．In the last paragraph, the author mainly ________.

　　A．talks about the intelligence of robots

　　B．explains how to create a world in space

　　C．describes what our future life might be

　　D．shows his worry about the environment

　　解析：选C　段落大意题。作者在本段中主要就人类未来的生活进行了简单地描绘，故选C项。

　　C

　　These are some ideas that some people came up with about what the life will be like in the year 2500.

　　We will have established a base on the moon. School kids can take field trips to the moon weekly. We will have found cures (疗法) for AIDS and cancer. The war will have ended and peace flows freely through the land. Kids will learn more and be smarter than ever before! History will be the main subject at school. Cafeteria (自助餐厅) food will be delicious! You just walk up to a machine, stick out your tongue, and it will scan your taste buds (味蕾) to see what you want to eat.

　　- Kristen

　　Here I am in the wonderful year of 2500 and life is so easy. I work in a pet store and it is so hard! I have to wake up at midnight every day and fly my car to the store. It takes so long to get there. It takes me 20 seconds to get to the store in Mississippi from my home in Florida! At work, I have to push 5 buttons and then I go home. It takes 2 seconds and that is like forever.

　　- Morgan

In the year 2500, I think we will have invented cars that run on things we don't need like