What was the immediate trigger of world war i? the sinking of the battleship maine the assassination of archduke franz ferdinand the sinking of the british passenger vessel the lusitania the german invasion of poland?

The immediate start of WWI was the assassination of the Archduke. A Serbian gang member, Gavrilo Princip, shot the Archduke, which really angered Austria, so Austria declared war on Serbia, which eventually led to WWI. The sinking of the Lusitania happened in 1915 and the German invasion of Poland was the start of WW2.