Read the passage below and choose the best answer ( A, B, C or D ) to each question.

 The habits of those who constantly play video games are very important to people working in video-game industry. If video games are going to one of the most attractive features of future interactive systems, it is essential for producers to know what types of games to make, how best to present such games on interactive video, and how to ensure that such games maintain their fascination for people. Above all, it is vital to build up detailed profiles of people who are addicted to video games.

 Until recently, the chief market for video games has been boys aged eight to fifteen. The fascination for interactive video games is seen in its purest form in this group. Video games appeal to some deep instinct in boys who find it impossible to tear themselves from them. Schoolwork is ignored, health is damaged and even eating habits are affected. Girls of the same age, however, are entirely different, demonstrating far greater freedom from the hold of video games. Quite simply, they can take video games in their strike, being able to play them when they want and then leave them alone.

Producers of video games are keen on __________.

• A. 
  finding the best ways of continuing to attract people
• B. 
  developing computer techniques in making such games
• C. 
  learning about drug to which people are addicted
• D. 
  designing ways