Play is the basic business of childhood, and more and more in recent years research has shown the great importance of play in the development of a human being.From earliest infancy  , every child needs opportunity and the right material for play, and the main tools of play are toys.The main function of toys is to suggest, encourage and assist play.To succeed in this, they must be good toys, which children will play with often, and will come back to again and again.Therefore, it is important to choose suitable toys for different stages of a child's development. In recent years research on infant development has shown that the standard a child is likely to reach, within the range of his inherited abilities, is largely determined in the first three years of his life.So a baby's ability to benefit from the right play materials should not be underestimated.A baby who is encouraged, talked to and shown things and played with, has the best chance of growing up successfully. The next stage, from three to five years old, curiosity knows no bounds.Every type of suitable toy should be made available to the child, for trying out, experimenting and learning, for discovering his own particular ability. Bricks and jigsaws and construction toys; painting, scribbling and making things; sand and water play; toys for imaginative and pretending play; the first social games for learning to play and get on with others. By the third stage of play development--from five to seven or eight years old-- the child is at school.But for a few more years play is still the best way of learning, at home or at school.It is easier to see which type of toys the child most enjoys. Until the age of seven or eight, play and work mean much the same to a child.But once reading has been mastered, then books and school become the main source of learning.Toys are still interesting and valuable, which lead up to new hobbies, but their significance has changed --to a child of nine or ten years old, toys and games mean, as to adults, relaxation and fun. 62. The passage tells us that children are the most curious when they are about  _  .
two years old one year old six years old four years old