The correct answer is D. Appeasement.
The policy of appeasement allowed for the Germans to build up their military and taking territory before the beginning of World War II.
Step-by-step explanation
The policy of appeasement was a conciliatory political position proposed by the Prime Minister of the United Kingdom Neville Chamberlain during the 1930s. As a result of this policy, Great Britain and France did not impose sanctions on Germany or Italy even though they had been involved in the Spanish civil war. In addition, this allowed Germany to rearm from 1933 forming a stronger army. On the other hand, Germany annexed Austrian territories during the year 1938. So, the correct answer is D. Appeasement.