穿上新的校服，走进新的教室，看见新的老师，遇到新的同学……一切都是新的，我们是中学生了。为了积极适应新的中学生活，我们要 （   ）
①课余时间去找小学同学玩，对不认识的同学敬而远之 ②自觉遵守规章制度 ③尽快建立新的人际关系 ④主动适应新的学习生活，迎接新的挑战

   Jane always goes to school early. She likes to talk to her friends before class. After school she does not go home early. She is always late. Jane stops to see the animals in the pet shop. She likes to see the dogs. One of them is a little white dog. She watches the little dog play in the window of the shop. She watches for a long time, so she comes home late.
   One day her father and mother ask why she is late, and she tells them about the little dog in the pet shop.
   Jane is not late the next day. She stops to look in the window of the shop. But she doesn’t see the dog, and she is very sad. She is also very happy, today is her birthday.
   Mother shows her a big birthday cake and Father gives her a birthday surprise(惊奇). He gives her the little white dog from the shop. Jane is very happy. The next day Jane does not come home late. She runs home to play with the white dog.

若函数y=(3-m)$x^{m^2-8}$是正比例函数，则常数m的值是（　　）

下列杂交组合属于测交的是                                (    )

给CH₃COOH、C₂H₅OH和浓硫酸的混合物加热，一段时间后，¹⁸O存在于