用下列方法除去含Ca^2＋、Mg^2＋、HCO₃^-、Cl^－的硬水，所得水含离子浓度最小的是(  )

Thousands of years ago，human(人类)didn’t live in towns．Sometimes they would live in caves(洞穴)or build camps in the forest．
Only about thirty people1 in each camp．The men would go hunting while the woman and children2food from trees around the camp．All the food was 3 among people in the group．Every few weeks they moved to another place to find more food．It was a simple life，but people had to be 4 .They had to make everything that they needed，and they had to know a lot about plants and animals．
Nowadays most people live in towns and cities，and they work in offices and factories．Life is 5than in the old days．There are fewer 6，but there is less excitement．Some people go7  excitement  sailing round the world．climbing mountains，or exploring(探测)caves．
Most people look forward to the8,a time when they can enjoy a change from the normal life．For some this means going camping．But camping today is 9 from camping in the past．Gas cookers，ready-made food and air-beds mean people can camp much more10 than they did in the old times．

大众希望的技术进步，既要方便也要实惠。顺应这种要求，我国已开始布局5G技术研发。相比4G每秒100MB的峰值速度，5G理论值将达到每秒10GB。这表明（    ）

①商品是使用价值和价值的统一

②消费意愿是物质生产的前提和基础

③消费可以引导生产的调整和升级

④科技含量高低决定了商品价值大小

下列说法中，不能证明地球是球体的说法是( )