A、They do not know what to learn. B、They are too young to concentrate their attention for a long time. C、They are occupied with

People have different views on what children should do at a very early age．Some think that children should begin their formal education and start to spend most of their time on studies．Others believe that it is still time for young children to play．Both views are based on respective ground．
(26)Those who argue for the playing time for children suggest that children at a very early age are still too young to focus their attention on learning．Their brain may not be ready for serious studies such as comprehension and memorizing learning materials．These people are partially right，for it is true that young children can hardly concentrate．Their attention on one thing lasts for no longer than 15 minutes or so．(27)But we can arrange classes for shorter periods，can’t we? And we can shift teaching subjects．Through putting them to study，young children are occupied with learning but not with playing．
(28)Those who argue for children’s early commencement for formal education believe that being put to studies，children can develop good habit of studying, for the process of learning helps develop children’s mental abilities like the ability to memorize，the ability to understand and the ability to do simple calculation．(28)Children’s habit of studying and love for learning are of great importance to youngsters because these two things set up the sound foundation for their future studies．
(29)Having children start formal education at a very early age benefits young children much more than simply letring them play most of their time．A good babit needs a long time to develop to become a second nature．More importantly，it is better to develop a good habit before a bad one may grow．