对计算机操作系统的作用描述完整的是( )。
A．管理计算机系统的全部软、硬件资源，合理组织计算机的工作流程，以达到充分发挥计算机资源的效率，为用户提供使用计算机的友好界面
B．对用户存储的文件进行管理，方便用户
C．执行用户键入的各类命令
D．它是为汉字操作系统提供运行的基础
参考答案：A
解析： 操作系统是管理、控制和监督计算机软、硬件资源协调运行的程序系统，由一系列具有不同控制和管理功能的程序组成，它是直接运行在计算机硬件上的、量基本的系统软件，是系统软件的核心。
Choose the words or expressions and complete the passage (选择最恰当的单词或词语，完成短文) 1．We have always been warned of the dangers of the forest fires. They cause 1 to a forest. They kill many plants and animals in an eco-system, which is a group of living things and their environment. But have you ever heard of a forest fire that can be 2 for a forest? 2．People start some of the fires with special reasons to actually do well to the eco-system. 3．In fact, fires are a natural part of any eco-system. Without fires, the oldest and largest trees would stop sunlight from reaching the forest floor. Fires can 3 some of these old trees. When the trees die, they provide something good for the earth. New trees can grow strong and healthy in their place. 4．Some trees even need fires to grow. These trees hold their seeds(种子) inside. Heats from a fire allow the coat of the seeds to open up. Then the seeds fall to the ground and have the 4 to grow. 5．Scientists, who know about nature’s needs, start some of these fires, called controlled burns. A fire is started and kept under control. This way, the fire does not spread out of the area or 5 a large space of the forest. Fires can be dangerous for animals. Even when animals continue to live after forest fires, they can go hungry 6 their food has been damaged in the fire. Small, controlled fires mean that animals will not have to move far to find food. After some time, small plants begin to grow. Animals return soon after the plants return. This 7 makes an eco-system. 6．So the next time you hear about a forest fire, think about the good as well as the bad. It may take a new eco-system a while to return, but it will likely come back stronger and healthier than ever.
|