Study method and Procedure Cross-Sectional Subject: Chinese population Children aged between 18 months and 6 years In the fieldtrips up to 19/06, we have interviewed 109 children Normal nurseries: 31 EETC(Heep Kong Society ): 78 (Among the 109 children, the demographic data of 17 children is not available)Study method and Procedure: • Cross-Sectional • Subject: – Chinese population – Children aged between 18 months and 6 years old – In the fieldtrips up to 19/06, we have interviewed 109 children. – Normal nurseries: 31 – EETC (Heep Kong Society): 78 – (Among the 109 children, the demographic data of 17 children is not available)