Read the passage carefully and choose the correct answers

In the 1960s, computers began to be used widely in industry for many purposes. They became common to be used for many different jobs within an organization. The first digital computers, with their large size and cost, mainly performed scientific calculations and often supported military objectives. They were used for helping in the design of the hydrogen bombs. Many of the most powerful computers available today are also used for nuclear weapons simulations. 

From the beginning, stored program computers were applied to business problems. Because the continual reductions in the cost and size, computers have been gradually used in smaller organizations. Moreover, with the invention of the microprocessor in the 1970s, it has become possible to produce inexpensive computers. In the 1980s, personal computers became popular for many tasks, including book-keeping, writing and printing documents, calculating forecasts and other repetitive mathematical tasks. 

As computers have become less expensive, they have been used extensively in the creative arts as well. Sound, pictures, and videos are now created and edited by computers. They have also been used for entertainment, with the video game becoming a huge industry. Computers have been used to control mechanical devices since they became small and cheap enough to do so. Today, it is almost rare to find a powered mechanical device not controlled by a computer. Perhaps the most famous computer-controlled mechanical devices are robots. Industrial robots have become common in mass production.

The text is about ___.

• A. 
  computer application
• B. 
  the invention of computers
• C. 
  robots
• D. 
  the invention of microprocessor