We should never give up ___________ others. Sometimes helping others means helping ourselves.

    I live in a small town near Xing'an in Guilin. You can't see it on the map of China, because it is too small. The air here is fresh(清新的). There are not many tall buildings in our town. The tallest building is in our school. There are four hundred students and twenty-five teachers in our school. In the front of the school, there is a playground. I often play basketball with my classmates on it. There is a little garden behind our school. And we can grow(种植) beautiful flowers and plant trees there. Next to the garden, there is an orange orchard(果园). You can hear birds singing everywhere. There is a river not far from our school. In summer, we usually go swimming with our teachers in it. We study Chinese, English, Maths and other subjects at school. The teachers are very nice. We love our school.

⑴向容器内倒入适量的水，水的体积记作V₁．

⑵将木块轻轻放入容器中，液面上升至V₂．

⑶用细针将木块按压，使木块浸没于水中，液面上升至V₃．请写出下列物理量的表达式：木块的质量m=____，木块的体积V=____，木块密度ρ=____ （已知水的密度为ρ_水）．

一个不透明的袋中只装有1个红球和2个篮球，它们除颜色外其余均相同．现随机从袋中摸出两个球，颜色是一红一蓝的概率是____.