读“青藏地区图”，回答下列问题．
下面是实验“绿叶在光下制造有机物”的方法步骤，其中有操作错误的是（ ）
①把盆栽的天竺葵放到黑暗处一昼夜
②用黑纸片把叶片一部分从上下两面遮盖
③把天竺葵放在阳光下照射
④一段时间后摘下叶片并去掉纸片
⑤将叶片放入盛有酒精的小烧杯中，用酒精灯加热小烧杯
⑥用清水漂洗叶片后滴加碘液，观察叶色变化．
看图，阅读短文，判断正误。
Tommy is a boy. He is apupil. He is a short and thin. He is ten. He gets up early every morning. He gets up at half past six. He brushes his teeth at a quarter to seven in the morning. He goes to school at half past seven in the morning.
同一平面内的三个力，大小分别为4 N、6 N、7 N，若三力同时作用于某一物体，则该物体所受三力合力的最大值和最小值分别为（ ）
He gets up early every morning. He gets up at half past six. 
He brushes his teeth at a quarter to seven in the morning. 
He goes to school at half past seven in the morning. 