Name：Lu Yang

Age：41

Job：Doctor

Family：Mrs Lu is an actress (女演员). They have two daughters. They are happy.

Name：Tian Yu

Age：6

Job：Student  

Family：His father is an actor. His mother is a singer(歌手). His sister Tian Miao is nine years old. She is a student too.

Name：Mary Green

Age：54

Job：An English teacher

Family：Her husband Jack is a hotel manager. They have two sons and a daughter.

一放在光滑水平面上的平板车，高为0.2m，质量为3m，平板车停靠在一光滑的四分之一圆弧轨道旁，平板车上表面刚好与圆弧轨道的最低点相切，一质量为m的物块从圆弧轨道上某点由静止释放，滑到圆弧轨道最低点时，对轨道的压力为2mg，物块滑上平板车后，再从平板车的右端滑离落到地面上时，离平板车右端的距离为s= $\frac{2}{15}$ m．已知物块与平板车间的动摩擦因数为μ=0.2，圆弧轨道的半径为R=0.4m，重力加速度为g=10m/s²，求：

用微粒的观点解释下列事实．

（1）碘固体（I₂）和碘蒸气都能使淀粉变蓝．

（2）等质量的碘固体和碘蒸气比较，碘蒸气的体积远大于碘固体．

①abc=0，②a+b+c>0，③b=3a, ④4ac—b²<0；其中正确的结论有（   ）