小明思考：能否用排空气的方法测量大米的体积呢？他设想将大米与空气密封在一个注射器内，只要测出注射器内空气和大米的总体积及空气的体积，其差值就是大米的体积。但如何测出空气的体积呢？

查 阅资料得知：温度不变时，一定质量气体的体积与其压强的乘积是定值。于是进行了实验二：称取5克大米并装入注射器内（如图丙），从注射器的刻度上读出大米和空气的总体积，通过压强传感器测出此时注射器内空气压强为P;而后将注射器内的空气缓慢压缩，当空气压强增大为2P时，再读出此时的总体积（压缩过程中 大米的体积、空气的温度均不变），整理相关数据记录如表。

 由实验二测得大米的密度为 ____  克／厘米³。（计算结果精确到0.01）

    This is my family tree. My name is Jack. I'm English. I have a big family. My wife(妻子) Allen is a teacher. We have two children. Tom is my son. Linda is my daughter. They are students in No. 2 Middle School. My father's name is Jeff. My mother's name is Grace. They are at home. Bill is my brother. He is a worker. Nancy is my wife's sister. She is a doctor. My wife's mother's name is Sue. Her father's name is Harry. They are old, too.

⑴____⑵____⑶____⑷____⑸____

关于质点，下列说法正确的是（   ）