Answer:
D. Euphemism.
Explanation:
A euphemism is the use of words in such a way that it 'conceals' or expresses an embarrassing, harsh, cruel, or offensive event. This means that certain words are used to make or express things in a more presentable manner to substitute an offensive or embarrassing situation.
In the given sentence, euphemism is used to talk about the Holocaust, the gas chambers, and the mass murder of millions of Jews. Since this historical event is a huge heartbreak and offensive in nature for the Jewish people, using the words such as "fire of anti-Semitism", "smolders", "smoke" all try to present the event as humanely as possible without sounding offensive.
Thus, the correct answer is option D.