东营地区石油储量丰富，为了测量某油井所产石油的密度，小刚收集了该井所产石油样品进行了如下测量（常温下石油为粘稠的液态）．

（1）将天平放在水平台上，调节好天平平衡．先用天平称出空烧杯的质量为31.2g．然后将石油样品倒入烧杯，放在调节好的天平左盘上称量，当天平重新平衡时，右盘中的砝码和游码的位置如图甲所示，则烧杯和石油样品的质量为____  g．

（2）将烧杯中的石油倒入量筒，其示数如图乙所示，石油的体积为____ mL．

（3）根据测量的数据，求得所测石油的密度为____ g/cm³．

（4）联想到某起石油泄漏事故中石油漂浮在水面上的情景，小刚发现自己测量的石油密度值偏大，你认为该实验方案造成测量结果偏大的原因是____ ．

（5）针对小刚的实验方案，请提出改进办法：____ ．

轮轴有____的作用。

人类常见的血型系统是____ 血型系统．人类的血型可分为　____ 、____ 、____ 、____ ．

①根据市场需求合理确定单车投放量

②加强管理，依法制裁破坏车辆的用户

③合理规划城市公共空间，引导用户有序停放车辆

④创新损坏车辆回收方式，促进资源循环利用

Dear Mum,

    I have studied abroad for some time. I miss you very much now.

    I 1 learned the famous saying “You don't know what you've got until it's gone.”Yes! Mill Li said her maths teacher made a huge difference in her life. But she was 2 because she had no chance to tell her teacher. This made me think a lot, especially 3 I'm thousands of kilometers away. I'm writing to you because I want you to know how 4 I love you.

    It's said that a 5 happiness was mostly because of their childhood. That's quite right. I still remember the times when you 6 my hand as we walked along. You told me stories about the brave elephant and encouraged me to be a 7 girl. … My childhood was filled with these warm memories.

    How time flies! There have been good times and bad times, but you were always by my side. When I won a prize, you smiled and felt proud 8 me. When I failed the exam, you comforted me. You always gave me courage to 9 all my difficulties.

    You've always said that we should judge（判断）people's 10 by how they live their lives every day. I think I'm now living a happy life. Thank you, Mum.

Love,

Feifei