Hint: The First World War started from 1914 and ended in 1918. It lasted for about four years and accused massive destruction and loss of life. World War I is regarded as one of the largest wars in history.
Complete answer: World War I began in the Balkans. 17 million people were dead and 20 million were wounded. The rival powers of Austria-Hungary against Britain, France and later the USA. Scholars tend to explain various causes of the First World War, the immediate one being the July Crisis or the Sarajevo crisis. The July Crisis is referred to as a period of an international emergency situation when the Archduke Franz Ferdinand of Austria -Hungary along with his wife were assassinated by Gavrillo Princip who was a member of the Serbian nationalist terrorist group called the Black Hand when the couple was in Sarajevo, in Bosnia which was a part of Austria-Hungary. The defence agreements that were made before World War I was:
a. Russia and Serbia
b. Germany and Austria-Hungary
c. France and Russia
d. Britain, France and Belgium
e. Japan and Britain
There were protests going on because Austria was in total control over the region. Serbia wanted to establish control over Bosnia and Herzegovina. This event resulted in Austria-Hungary declaring war on Serbia. Having an alliance with Serbia, Russia also started mobilising its forces. Seeing this Germany attacked Russia. This led to a worldwide expansion of the war.
Option D is the correct answer.
Note: The assassination of Archduke Franz Ferdinand was the catalyst that started the First World War. A major reason was imperialism too. Before the war countries in Asia and Africa were under European control. One of the chief reasons being the export of raw materials. The increasing confrontation and desire for greater control over territories led to the First World War.