Give one cause of World War I. Explain what it is and how it led to the war.

One cause of World War l was the assassination with   Austrian Archduke Franz Ferdinand

Explanation: After that you had in July 28 - Austria who declared war on Serbia then in August 1- you had Germany which had or as  Austria ally that declared war on Russia, who was ally of Serbia. and so on with Germany that declared war on France, great Britain (ally of France, that declared war against Germany. Then at the time President Wilson declares United States will remain neutral.

yellow fever and other tropical diseases

the answer is a) to be able to obey them.