30. B. Because they want their children to be well prepared for their future.
Dẫn chứng: For this reason, many parents want their children, often as young as ten months old, to become familiar with computers. They seem to think that if their children grow up with computers, they will be better equipped to face the challenges of the future.
31. D. when they hold and feel things around them.
Dẫn chứng: Children gain valuable experience of the world from their interaction with physical objects. Ten-month-old babies may benefit more from bumping their heads or putting various objects in their mouths than they will from staring at eye-catching cartoons. A four-year-old child can improve hand-eye coordination and understand cause and effect better by experimenting with a crayon than by moving a cursor around a computer screen.