Answer: Francis Joseph
Explanation: At a time when a blank check was sent by William II, which was on July 6, 1914, Franz Ferdinand was already dead.
Namely, after the assassination in Sarajevo, Count Leopold von Berchtold, the Austria-Hungarian Foreign Minister, wrote a letter in the name of Emperor Francis Joseph, whom the Emperor personally signed and sent to Emperor William II, where he sought support, and intends to bring all the blame to Serbia. On July 6, 1914, William (Wilhelm) II, German Emperor, sent the so-called "blank check" informing Francis Josef that Austria Hungary could rely on Germany and that literally any action would be supported against Serbia, and that's why this famous response was called blank check.