1) The word "mountain" contains three vowels: O, U, and A.

2) The rise of remote work and digital transformation has been accelerated by the COVID-19 pandemic, leading to changes in work dynamics, reliance on digital technologies, and the reimagining of traditional office spaces.

3) The Industrial Revolution led to significant urbanization, as people migrated from rural areas to cities in search of employment in factories.

4) The ozone layer, located in the Earth's stratosphere, protects us from harmful ultraviolet (UV) radiation.