Question

what changes happened in 20th century

Answer 1

The 20th century was a century that began on January 1, 1901 and ended on December 31, 2000. It was the tenth and final century of the 2nd millennium. It is distinct from the century known as the 1900s which began on January 1, 1900 and ended on December 31, 1999.

Answer 2

pollution and many newly discovered diseases and improvement of technology