被誉为“海上丝绸之路”见证﹣宋代沉船“南海一号”，被成功打捞出海．“南海一号”沉没于水下20m深，受到海水的压强为　____ 　Pa，亚洲第一吊“华天龙”缓慢吊起沉船，沉船出水前，受到的浮力____ （填“变大”、“变小”或“不变”），这艘宋代古船排水量（船满载时的总质量）为600吨，则古船在满载时受到的浮力为　____ 　N．（g=10N/kg，海水的密度为1.03×10³kg/m³）

    Bill is an English boy. He is twelve. He lives in China with his family. There are four people in his family. They are his father Jack Cliton, his mother Catherine and his little sister Abby. He has a yellow dog. Its name is Barbi. His father is mending his bike. What is Bill doing? Ah, he is doing Chinese homework. He can't speak Chinese very well. But he loves Chinese very much. Bill's father works in middle school. He is an English teacher. His mother is in a TV factory. Bill and his sister go to the same school.

如图是“探究磁场对通电直导线的作用”实验装置，完成下面各小题：

The drivers have to _______ the traffic rules and control themselves if they want to be safe on the road.