The western democracies responded to aggression with a policy of appeasement because the Western democracies wanted to avoid the horrors of another war. Option C is correct.
In other words, they did not want to interfere militarily with Nazi land grabs, believing that if they gave Hitler what he wanted, they could stave off a new devastating world war.
So, appeasement may be defined as the policy of making concessions to the dictatorial powers in order to avoid conflict.