[单项选择] Human beings have used tools for a very long time. In some parts of the world you can still find tools that people used more than two million years ago. They made these tools by hitting one stone against another. In this way they broke off pieces from one of the stones. These chips of stone were usually sharp on one side. People used them for cutting meat and skin from dead animals, and also for making other tools out of wood. Human beings needed to use tools because they did not have sharp teeth like other meat-eating animals, such as lions and tigers. Tools helped people to get food more easily. Working with tools also helped to develop human intelligence. The human brain grew bigger, and human beings began to invent more and more tools and machines. The stone chip was one of the first tools that people used, and perhaps it is the most important. Some scientists say that it was the key to the success of mankind. Since 1960 a new kind of tool has appeared. This is the si
A. was one of the first tools.
B. developed human capabilities.
C. led to the invention of machines.
D. was crucial to the development of mankind.

[单项选择] Human beings have used tools for a very long time. In some parts of the world you can still find tools that people used more than two million years ago. They made these tools by hitting one stone against another. In this way they broke off pieces from one of the stones. These chips of stone were usually sharp on one side. People used them for cutting meat and skin from dead animals, and also for making other tools out of wood. Human beings needed to use tools because they did not have sharp teeth like other meat-eating animals, such as lions and tigers. Tools helped people to get food more easily. Working with tools also helped to develop human intelligence. The human brain grew bigger, and human beings began to invent more and more tools and machines. The stone chip was one of the first tools that people used, and perhaps it is the most important. Some scientists say that it was the key to the success of mankind. Since 1960 a new kind of tool has appeared. This is the si
A. disastrous.
B. unpredictable.
C. exciting.
D. colourful.

[单项选择]
Human beings have used tools for a very long time. In some parts of the world you can still find tools that people used more than two million years ago. They made these tools by hitting one stone against another. In this way they broke off pieces from one of the stones. These chips of stone were usually sharp on one side. People used them for cutting meat and skin from dead animals, and also for making other tools out of wood. Human beings needed to use tools because they did not have sharp teeth like other meat-eating animals, such as lions and tigers. Tools helped people to get food more easily.
Working with tools also helped to develop human intelligence. The human brain grew bigger, and human beings began to invent more and more tools and machines. The stone chip was one of the first tools that people used, and perhaps it is the most important. Some scientists say that it was the key to the success of man
A. Human beings didn’t have sharp teeth like other meat-eating animals and tools helped them to get food more easily.
B. Tools helped to develop human intelligence.
C. Tools helped the human beings to cut meat and skin from dead animals.
D. It was easy to make stone tools.

[单项选择]The human beings have polluted the environment seriously. It is time the United Nations must take some measures.
A. take
B. taking
C. to take
D. took

[单项选择]

Human beings have eaten apples for millions of years. Scientists agree that 85 percent of apples is water and they can grow in almost everywhere except the hottest and the coldest places. As is known to all, China and the United States are the two major countries in producing apples.
There are a great variety of apples. Surprisingly, the majority of apples are for sale without any processing. Various sorts of apples are grown in the US, among which Delicious, Golden Delicious, and Mclntosh are the most common ones.
Apples are different from each other in color, taste and size. The color of the skin might be green, red or yellow. They have a wide range of sizes, among which Delicious apples are the largest. The taste might be divided into two categories: sweet or sour (酸的) . Generally speaking, sweet apples are eaten while sour apples are utilized to make applesauce (苹果酱).
Apple trees may grow to thirteen meters, They grow best in those areas where winters
A. produced
B. grown
C. improved
D. sold