保存食品的方法主要有物理的方法____和____.
图中的两个容器中盛有同种相同质量的液体,容器底部受到液体的压强分别为PA、PB,容器底部受到液体的压力分别为FA、FB,则
-My parents our home for a few hours when I arrived. I didn't meet them.-You could call them if you wanted to know where they were.
下列过程只发生物理变化的是( )