Computer.

Nowadays, science-technology develops very strongly. So human's life is equiped fully with modern equipments such as: mobile phone, car, air condition... But, any thing also has advantages and disavantages. For example, the car are very useful in movement. However,they are the reason of environmental polution. There is device very neccessary in stydying as well as working. Do you know it? Yes, it's a computer. Of course, it also has advantages and disadvantages.