The correct answer is Option C) A food shortage in Germany.
The Royal Navy's Blockade led to sever food shortages in Germany during World War I.
The blockade lasted from 1914 to 1919 with the intent of limited the supply lines of the Central powers of the war. This included Germany, Austria-Hungary and the Ottoman Empire.
Most European countries relied on imported food and most of this came from the United States across the Atlantic Ocean.
Hence, both Germany and the United Kingdom tried to blockade one another.