The correct option is A Danzig Corridor
Polish Corridor, also known as the Danzig Corridor, strip of land, 20 to 70 miles (32 to 112 km) wide, that gave the newly reconstituted state of Poland access to the Baltic Sea after World War I. The corridor lay along the lower course of the Vistula River and consisted of West Prussia and most of the province of Posen (Poznań), which the Treaty of Versailles (1919) transferred from defeated Germany to Poland. Hence, Option A is correct. According to the Treaty of Versailles, the Rhineland, a strip of land inside Germany bordering on France, Belgium and the Netherlands, was to be de-militarised. That is, no German troops were to be stationed inside that area or any fortifications built. As part of the Treaty of Versailles which gave the Saar to the League of Nations, it stated that there should be a vote or plebiscite to decide who should rule the Saar in the future. In 1935, the Saar region voted 90% in favour of returning to Germany. Germany was forced to return Alsace-Lorraine to France. Since none of the other territories were returned to Poland, these are incorrect.