It was Saturday. Mike stayed at home alone(单独地). His parents went to visit his grandparents in another city. He did his homework and read books. After lunch, he watched TV and played basketball on the playground with Jack. He felt very tired. In the evening, his parents came back and brought him some presents. They were a schoolbag and a basketball. Mike felt very excited!

在我们的学习生活中，要真正做到尊重他人，就必须（  ）

①懂得不尊重他人就不可能赢得他人的尊重     ②关注他人的尊严 

③要从欣赏、鼓励、期望等角度来善待他人     ④不做有损他人尊严的事

生物检索表常用来鉴定生物的种类．请利用这张简单的“脊椎动物检索表”，鉴定出下列动物中属于S类动物的是（    ）

1a 体外长有毛皮，胎生…哺乳类

1b 体外没有毛皮，卵生…2

2a 体外长有羽毛，体温恒定…R类

2b 体外无羽毛，体温不恒定…3

3a 表皮干燥，在陆地上产卵…S类

3b 皮肤湿润，在水中产卵…4．