只有团结友爱，共同进步，才能使集体更加美好和谐。下列行为有利于同学之间团结友爱、共同进步的是（    ）

①放学后，经常邀请同学去网吧玩游戏                      ②同学不开心时，主动帮其排忧解难

③同学不能完成作业时，热情主动让其抄自己的      ④班干部对违反纪律的同学，及时予以提醒

有3个正方形如图所示放置，阴影部分的面积依次记为S₁，S₂，则S₁：S₂等于（  ）

    I'm Peter. There are four people in my family. They are my father, my mother, my grandfather and me. I'm twelve. My birthday is on 15th March. My parents are both doctors. They help people. Their birthdays are both in May. My grandfather is old. He is sixty-five. His birthday is on 9th June. He likes reading. I like reading too. I want to be a teacher in the future. I want to teach Chinese in a school.