Answer:
Metaphor
Step-by-step explanation:
A metaphor is a figure of speech that asserts that one element is similar or equal to another element without using the words “like” or “as.” It is an implied comparison that is often used to make the writing or speech more colorful and interesting and to give new insights. The phrase “petroleum morgue” is a metaphor: it implicitly compares the word “petroleum” to something extremely dark, suggesting that the morgue was extremely dark.