下列有关新型高分子材料的说法中不正确的是（　　）

一质量为0.5kg的小球，用长为0.4m细绳拴住，在竖直平面内做圆周运动（g取10m/s²）．求

Safety must come first. During the coming summer vacation, some of us may travel to other places. To keep safe during the journey, we should      .  

     ①avoid eating raw(生的)and cold food

     ②obey the local traffic rules

     ③swim in the dangerous area

     ④never stretch our hands out of the window when taking a bus

     ⑤ tell strangers our personal information

Please post this letter in the post office nearby, and __________, I will get two tickets in the train station. （   ）