Choose the item (A, B, C or D) that best completes the following sentences

One of the greatest advantages of robots is that they can work in situations that are dangerous or harmful for human workers. For example, the continuous smell of paint has a harmful effect on painters, but it doesn't "bother" a robot. Robots can work in nuclear power plants and in undersea research stations that might be dangerous for humans. Already, robots are working in the plastics industry and in chemical and industrial equipment industries. One  of the most common uses of robots is still in automobile factories. They can do the heavy, unpleasant, or dangerous work. These kinds of industrial robots are not usually "mobile". The work they need to do is brought to them, like cars on an assembly line, for example.

The robot industry is a big business. By the middle of the 1990s, Japan' led the world in robot production with more than 71,000 industrial robots at work. Both the United States and Japan, as well as other countries, continue to develop more advanced robots. Robots can now be made to perform more complex jobs. Robots can make decisions while they are working  and learn from their mistakes. Robots can now see with TV camera "eyes." They can easily hear and can even speak using a voice made by a computer. But it is difficult to make a robot "understand." Thinking and understanding are very human qualities. The robots of the future will probably be very complex. They will be able to perform many humanlike tasks. Robots and other technology will make the future a very interesting place!

We can infer from the passage that by the middle of  the 1990s ............

• A. 
  only Japan had used robots in production
• B. 
  Japan and the USA were the only countries to use robots
• C. 
  some countries had used robots in industrial production
• D. 
  Japan led the world in production thanks to robots