Alkynes play an important role in organic chemistry.

Alkenes play an important role in organic chemistry.

Alkenes play an important role in organic chemistry.

Alkanes are basic components of organic chemistry.

He is studying the history of African Americans.

The parasympathetic nervous system helps our body to relax and conserve energy.

The Empire of Japan, written as 大日本帝國 in Kyūjitai, was a nation that existed from 1868 to 1945.

The Imperial Japanese Army was a Japanese military force that existed from the Meiji era to the Showa era.

The Imperial Japanese Navy was once the navy of Japan.

World War I was a large-scale war that lasted from 1914 to 1918.