王叔叔要去美国做生意，临行前大家纷纷给他提建议，你觉得哪些建议有道理（   ）

①美国人吃饭用刀叉，你带上筷子，还有山西老陈醋，吃相文雅点，声音不要太大  

②你英语不行，人生地不熟的，美国人又傲慢，除了谈生意，少和他们来往

③要入乡随俗，尊重对方的文化和习惯，对人热情些，但不要低三下四

④要有开放的心态，不要只在华人圈内交往，多参加公益活动，主动融入当地社会

青春期是人一生中身体发育的重要时期，这一时期我们的身体发生很大变化。下面的选项中不属于青春期生理变化的是（    ）

⊙O的半径为2，点P是⊙O外一点，OP的长为3，那么以P为圆心，且与⊙O相切的圆的半径一定是(       )

    We eat food with the help of hands every day. It is possible for some germs(细菌) to get into our bodies. So it is important to know how to wash hands in the right way.

    A piece of news from CCTV says that students from Guangzhou have a good way of learning how to wash hands. They learn it through doing hands-washing exercises during the ①break. The teachers there say most students wouldn't like to listen but they like to act. So now the students are interested in the interesting exercises. They are learning carefully. ②They want to be teachers for their parents and friends after they learn them well.