“她们不是1个人在战斗，靠的是12个人的集体努力”“技术专业、实力过硬、拧成一股绳，这就是团队的力量”……里约奥运会的圣火已经熄灭，但在社交网络上，人们对女排精神的思考仍在延续。女排夺冠，是每个人团结奋进的结果，更是集体主义精神的最好诠释。最是团结见力量。中国女排用实绩告诉人们，集体主义精神永远不会过时。

①橡皮帽对笔尖有保护作用；

②笔尾的油能防止墨水的蒸发；

③使用水笔时，笔中的墨水与油在大气压的作用下向笔尖流动；

④使用水笔时，笔尖与纸之间的摩擦为滚动摩擦．

其中合理的（   ）

    Bird lovers know that a good place to go bird-watching is Guandu Nature Park. As many as 220 kinds of birds come to this park every year. Since the park offers birds lots of food to eat and places to build their nests, it has become a paradise（天堂）for birds.

    Guandu Nature Park is also a great outdoor classroom. The park's Nature Center provides guided tours to the public. During the tour, visitors can learn about the environment. So, if you want to have a fun and educational weekend, come to Guandu Nature Park. Get away from city life and head into nature.