During which era did people move to cities and create instrumental pieces of technology?

As water is cooled from 4 c to 0 c its density

The declining axolotl population in mexico city is an example of in overcrowded cities. a. the surpassing of support capacity b. changes to natural environments and native species c. the lack of safe homes and tenured spaces d. the effects of a growing urban heat island

Following the new zealand wars, the british government